diff --git a/src/main/java/org/onosproject/yangutils/datamodel/YangDataTypes.java b/src/main/java/org/onosproject/yangutils/datamodel/YangDataTypes.java
index bf77059..4edf482 100644
--- a/src/main/java/org/onosproject/yangutils/datamodel/YangDataTypes.java
+++ b/src/main/java/org/onosproject/yangutils/datamodel/YangDataTypes.java
@@ -217,5 +217,21 @@
     /**
      * Derived Data type.
      */
-    DERIVED
+    DERIVED;
+
+    /**
+     * Returns YANG data type for corresponding type name.
+     *
+     * @param name type name from YANG file.
+     * @return YANG data type for corresponding type name.
+     */
+    public static YangDataTypes getType(String name) {
+        name = name.replace("\"", "");
+        for (YangDataTypes yangDataType : values()) {
+            if (yangDataType.name().equalsIgnoreCase(name)) {
+                return yangDataType;
+            }
+        }
+        return YangDataTypes.DERIVED;
+    }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/YangUtilsParserManager.java b/src/main/java/org/onosproject/yangutils/parser/impl/YangUtilsParserManager.java
index dcab33a..1fcf0b8 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/YangUtilsParserManager.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/YangUtilsParserManager.java
@@ -36,6 +36,8 @@
  */
 public class YangUtilsParserManager implements YangUtilsParser {
 
+    public static final int SUB_STATEMENT_CARDINALITY = 1;
+
     @Override
     public YangNode getDataModel(String yangFile) throws IOException, ParserException {
 
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ConfigListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ConfigListener.java
index f5855e8..f68b165 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ConfigListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ConfigListener.java
@@ -16,8 +16,19 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -55,18 +66,41 @@
      */
     public static void processConfigEntry(TreeWalkListener listener,
                                              GeneratedYangParser.ConfigStatementContext ctx) {
-        // TODO method implementation
-    }
+        boolean isConfig = false;
 
-    /**
-     * It is called when parser exits from grammar rule (config), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processConfigExit(TreeWalkListener listener,
-                                            GeneratedYangParser.ConfigStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.CONFIG_DATA, "", ListenerErrorLocation.ENTRY);
+
+        if (ctx.TRUE_KEYWORD() != null) {
+            isConfig = true;
+        }
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        switch (tmpData.getParsableDataType()) {
+            case LEAF_DATA:
+                YangLeaf leaf = (YangLeaf) tmpData;
+                leaf.setConfig(isConfig);
+                break;
+            case CONTAINER_DATA:
+                YangContainer container = (YangContainer) tmpData;
+                container.setConfig(isConfig);
+                break;
+            case LEAF_LIST_DATA:
+                YangLeafList leafList = (YangLeafList) tmpData;
+                leafList.setConfig(isConfig);
+                break;
+            case LIST_DATA:
+                YangList yangList = (YangList) tmpData;
+                yangList.setConfig(isConfig);
+                break;
+            case CHOICE_DATA: // TODO
+                break;
+            default:
+                throw new ParserException(ListenerErrorMessageConstruction
+                        .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                ParsableDataType.CONFIG_DATA,
+                                "", ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
index b77f594..e330350 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
@@ -15,9 +15,20 @@
  */
 
 package org.onosproject.yangutils.parser.impl.listeners;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.parser.Parsable;
 
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -54,6 +65,8 @@
  */
 public final class ContainerListener {
 
+    private static ParsableDataType yangConstruct;
+
     /**
      * Creates a new container listener.
      */
@@ -70,7 +83,44 @@
      */
     public static void processContainerEntry(TreeWalkListener listener,
                                              GeneratedYangParser.ContainerStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.CONTAINER_DATA, String.valueOf(ctx.IDENTIFIER().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        boolean result = validateSubStatementsCardinality(ctx);
+        if (!result) {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_CARDINALITY,
+                            yangConstruct, "", ListenerErrorLocation.ENTRY));
+        }
+
+        YangContainer container = new YangContainer();
+        container.setName(ctx.IDENTIFIER().getText());
+
+        Parsable curData = listener.getParsedDataStack().peek();
+
+        if (curData instanceof YangNode) {
+            YangNode curNode = (YangNode) curData;
+            try {
+                curNode.addChild(container);
+            } catch (DataModelException e) {
+                throw new ParserException(ListenerErrorMessageConstruction
+                        .constructExtendedListenerErrorMessage(ListenerErrorType.UNHANDLED_PARSED_DATA,
+                                ParsableDataType.CONTAINER_DATA,
+                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                ListenerErrorLocation.ENTRY,
+                                e.getMessage()));
+            }
+            listener.getParsedDataStack().push(container);
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.CONTAINER_DATA,
+                            String.valueOf(ctx.IDENTIFIER().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
     }
 
     /**
@@ -82,6 +132,61 @@
      */
     public static void processContainerExit(TreeWalkListener listener,
                                             GeneratedYangParser.ContainerStatementContext ctx) {
-        //TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.CONTAINER_DATA, String.valueOf(ctx.IDENTIFIER().getText()),
+                ListenerErrorLocation.EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangContainer) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.CONTAINER_DATA,
+                            String.valueOf(ctx.IDENTIFIER().getText()),
+                            ListenerErrorLocation.EXIT));
+        }
+    }
+
+    /**
+     * Validates the cardinality of container sub-statements as per grammar.
+     *
+     * @param ctx context object of the grammar rule.
+     * @return true/false validation success or failure.
+     */
+    public static boolean validateSubStatementsCardinality(GeneratedYangParser.ContainerStatementContext ctx) {
+
+        if ((!ctx.presenceStatement().isEmpty())
+                && (ctx.presenceStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.PRESENCE_DATA;
+            return false;
+        }
+
+        if ((!ctx.configStatement().isEmpty())
+                && (ctx.configStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.CONFIG_DATA;
+            return false;
+        }
+
+        if ((!ctx.descriptionStatement().isEmpty())
+                && (ctx.descriptionStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.DESCRIPTION_DATA;
+            return false;
+        }
+
+        if ((!ctx.referenceStatement().isEmpty())
+                && (ctx.referenceStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.REFERENCE_DATA;
+            return false;
+        }
+
+        if ((!ctx.statusStatement().isEmpty())
+                && (ctx.statusStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.STATUS_DATA;
+            return false;
+        }
+
+        return true;
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/DescriptionListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/DescriptionListener.java
index 71250b4..a328cb7 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/DescriptionListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/DescriptionListener.java
@@ -16,8 +16,16 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangDesc;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -51,18 +59,22 @@
      */
     public static void processDescriptionEntry(TreeWalkListener listener,
                                              GeneratedYangParser.DescriptionStatementContext ctx) {
-        // TODO method implementation
-    }
 
-    /**
-     * It is called when parser exits from grammar rule (description), it perform
-     * validations and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processDescriptionExit(TreeWalkListener listener,
-                                            GeneratedYangParser.DescriptionStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.DESCRIPTION_DATA, String.valueOf(ctx.string().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        if (tmpData instanceof YangDesc) {
+            YangDesc description = (YangDesc) tmpData;
+            description.setDescription(ctx.string().getText());
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.DESCRIPTION_DATA,
+                            String.valueOf(ctx.string().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/KeyListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/KeyListener.java
index 8cd271a..32677a5 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/KeyListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/KeyListener.java
@@ -16,8 +16,16 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -51,18 +59,30 @@
      */
     public static void processKeyEntry(TreeWalkListener listener,
                                          GeneratedYangParser.KeyStatementContext ctx) {
-        // TODO method implementation
-    }
 
-    /**
-     * It is called when parser exits from grammar rule (key), it perform
-     * validations and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processKeyExit(TreeWalkListener listener,
-                                        GeneratedYangParser.KeyStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.KEY_DATA, String.valueOf(ctx.string().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        if (listener.getParsedDataStack().peek() instanceof YangList) {
+            YangList yangList = (YangList) tmpData;
+            String tmpKeyValue = ctx.string().getText().replace("\"", "");
+            if (tmpKeyValue.contains(" ")) {
+                String[] keyValues = tmpKeyValue.split(" ");
+                for (String keyValue : keyValues) {
+                    yangList.addKey(keyValue);
+                }
+            } else {
+                yangList.addKey(tmpKeyValue);
+            }
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.KEY_DATA,
+                            String.valueOf(ctx.string().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListener.java
index 721434c..829dd10 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListener.java
@@ -16,8 +16,18 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangLeavesHolder;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -52,6 +62,8 @@
  */
 public final class LeafListListener {
 
+    private static ParsableDataType yangConstruct;
+
     /**
      * Creates a new leaf list listener.
      */
@@ -68,7 +80,36 @@
      */
     public static void processLeafListEntry(TreeWalkListener listener,
                                             GeneratedYangParser.LeafListStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.LEAF_LIST_DATA, String.valueOf(ctx.IDENTIFIER().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        boolean result = validateSubStatementsCardinality(ctx);
+        if (!result) {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_CARDINALITY,
+                            yangConstruct, "", ListenerErrorLocation.ENTRY));
+        }
+
+        YangLeafList leafList = new YangLeafList();
+        leafList.setLeafName(ctx.IDENTIFIER().getText());
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        YangLeavesHolder leaves;
+
+        if (tmpData instanceof YangLeavesHolder) {
+            leaves = (YangLeavesHolder) tmpData;
+            leaves.addLeafList(leafList);
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.LEAF_LIST_DATA,
+                            String.valueOf(ctx.IDENTIFIER().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
+        listener.getParsedDataStack().push(leafList);
     }
 
     /**
@@ -80,6 +121,80 @@
      */
     public static void processLeafListExit(TreeWalkListener listener,
                                            GeneratedYangParser.LeafListStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.LEAF_LIST_DATA, String.valueOf(ctx.IDENTIFIER().getText()),
+                ListenerErrorLocation.EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangLeafList) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.LEAF_LIST_DATA,
+                            String.valueOf(ctx.IDENTIFIER().getText()),
+                            ListenerErrorLocation.EXIT));
+        }
+    }
+
+    /**
+     * Validates the cardinality of leaf-list sub-statements as per grammar.
+     *
+     * @param ctx context object of the grammar rule.
+     * @return true/false validation success or failure.
+     */
+    public static boolean validateSubStatementsCardinality(GeneratedYangParser
+            .LeafListStatementContext ctx) {
+
+        if (ctx.typeStatement().isEmpty()
+                || (ctx.typeStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.TYPE_DATA;
+            return false;
+        }
+
+        if ((!ctx.unitsStatement().isEmpty())
+                && (ctx.unitsStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.UNITS_DATA;
+            return false;
+        }
+
+        if ((!ctx.configStatement().isEmpty())
+                && (ctx.configStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.CONFIG_DATA;
+            return false;
+        }
+
+        if ((!ctx.maxElementsStatement().isEmpty())
+                && (ctx.maxElementsStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.MAX_ELEMENT_DATA;
+            return false;
+        }
+
+        if ((!ctx.minElementsStatement().isEmpty())
+                && (ctx.minElementsStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.MIN_ELEMENT_DATA;
+            return false;
+        }
+
+        if ((!ctx.descriptionStatement().isEmpty())
+                && (ctx.descriptionStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.DESCRIPTION_DATA;
+            return false;
+        }
+
+        if ((!ctx.referenceStatement().isEmpty())
+                && (ctx.referenceStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.REFERENCE_DATA;
+            return false;
+        }
+
+        if ((!ctx.statusStatement().isEmpty())
+                && (ctx.statusStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.STATUS_DATA;
+            return false;
+        }
+
+        return true;
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListener.java
index ae8c9f6..2de3344 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListener.java
@@ -20,8 +20,18 @@
  */
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.datamodel.YangLeavesHolder;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -55,6 +65,8 @@
  */
 public final class LeafListener {
 
+    private static ParsableDataType yangConstruct;
+
     /**
      * Creates a new leaf listener.
      */
@@ -71,7 +83,37 @@
      */
     public static void processLeafEntry(TreeWalkListener listener,
                                         GeneratedYangParser.LeafStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.LEAF_DATA, String.valueOf(ctx.IDENTIFIER().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        boolean result = validateSubStatementsCardinality(ctx);
+        if (!result) {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_CARDINALITY,
+                            yangConstruct, "", ListenerErrorLocation.ENTRY));
+        }
+
+        YangLeaf leaf = new YangLeaf();
+        leaf.setLeafName(ctx.IDENTIFIER().getText());
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        YangLeavesHolder leaves;
+
+        if (tmpData instanceof YangLeavesHolder) {
+            leaves = (YangLeavesHolder) tmpData;
+            leaves.addLeaf(leaf);
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.LEAF_DATA,
+                            String.valueOf(ctx.IDENTIFIER().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
+
+        listener.getParsedDataStack().push(leaf);
     }
 
     /**
@@ -83,6 +125,74 @@
      */
     public static void processLeafExit(TreeWalkListener listener,
                                        GeneratedYangParser.LeafStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.LEAF_DATA, String.valueOf(ctx.IDENTIFIER().getText()),
+                ListenerErrorLocation.EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangLeaf) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.LEAF_DATA,
+                            String.valueOf(ctx.IDENTIFIER().getText()),
+                            ListenerErrorLocation.EXIT));
+        }
+    }
+
+    /**
+     * Validates the cardinality of leaf sub-statements as per grammar.
+     *
+     * @param ctx context object of the grammar rule.
+     * @return true/false validation success or failure.
+     */
+    public static boolean validateSubStatementsCardinality(GeneratedYangParser
+            .LeafStatementContext ctx) {
+
+        if (ctx.typeStatement().isEmpty()
+                || (ctx.typeStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.TYPE_DATA;
+            return false;
+        }
+
+        if ((!ctx.unitsStatement().isEmpty())
+                && (ctx.unitsStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.UNITS_DATA;
+            return false;
+        }
+
+        if ((!ctx.configStatement().isEmpty())
+                && (ctx.configStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.CONFIG_DATA;
+            return false;
+        }
+
+        if ((!ctx.mandatoryStatement().isEmpty())
+                && (ctx.mandatoryStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.MANDATORY_DATA;
+            return false;
+        }
+
+        if ((!ctx.descriptionStatement().isEmpty())
+                && (ctx.descriptionStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.DESCRIPTION_DATA;
+            return false;
+        }
+
+        if ((!ctx.referenceStatement().isEmpty())
+                && (ctx.referenceStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.REFERENCE_DATA;
+            return false;
+        }
+
+        if ((!ctx.statusStatement().isEmpty())
+                && (ctx.statusStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.STATUS_DATA;
+            return false;
+        }
+
+        return true;
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
index 7aceab6..82d69cb 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
@@ -16,8 +16,20 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNodeType;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -56,6 +68,8 @@
  */
 public final class ListListener {
 
+    private static ParsableDataType yangConstruct;
+
     /**
      * Creates a new list listener.
      */
@@ -72,7 +86,44 @@
      */
     public static void processListEntry(TreeWalkListener listener,
                                              GeneratedYangParser.ListStatementContext ctx) {
-        // TODO
+
+        YangNode curNode;
+
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.LIST_DATA, String.valueOf(ctx.IDENTIFIER().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        boolean result = validateSubStatementsCardinality(ctx);
+        if (!result) {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_CARDINALITY,
+                            yangConstruct, "", ListenerErrorLocation.ENTRY));
+        }
+
+        YangList yangList = new YangList(YangNodeType.LIST_NODE);
+        yangList.setName(ctx.IDENTIFIER().getText());
+
+        Parsable curData = listener.getParsedDataStack().peek();
+        if (curData instanceof YangNode) {
+            curNode = (YangNode) curData;
+            try {
+                curNode.addChild(yangList);
+            } catch (DataModelException e) {
+                throw new ParserException(ListenerErrorMessageConstruction
+                        .constructExtendedListenerErrorMessage(ListenerErrorType.UNHANDLED_PARSED_DATA,
+                                ParsableDataType.LIST_DATA,
+                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                ListenerErrorLocation.ENTRY,
+                                e.getMessage()));
+            }
+            listener.getParsedDataStack().push(yangList);
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.LIST_DATA,
+                            String.valueOf(ctx.IDENTIFIER().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
     }
 
     /**
@@ -84,6 +135,77 @@
      */
     public static void processListExit(TreeWalkListener listener,
                                             GeneratedYangParser.ListStatementContext ctx) {
-        // TODO
+
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.LIST_DATA, String.valueOf(ctx.IDENTIFIER().getText()),
+                ListenerErrorLocation.EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangList) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.LIST_DATA,
+                            String.valueOf(ctx.IDENTIFIER().getText()),
+                            ListenerErrorLocation.EXIT));
+        }
+    }
+
+    /**
+     * Validates the cardinality of list sub-statements as per grammar.
+     *
+     * @param ctx context object of the grammar rule.
+     * @return true/false validation success or failure.
+     */
+    public static boolean validateSubStatementsCardinality(GeneratedYangParser.ListStatementContext ctx) {
+
+        if ((!ctx.keyStatement().isEmpty())
+                && (ctx.keyStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.KEY_DATA;
+            return false;
+        }
+
+        if ((!ctx.configStatement().isEmpty())
+                && (ctx.configStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.CONFIG_DATA;
+            return false;
+        }
+
+        if ((!ctx.maxElementsStatement().isEmpty())
+                && (ctx.maxElementsStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.MAX_ELEMENT_DATA;
+            return false;
+        }
+
+        if ((!ctx.minElementsStatement().isEmpty())
+                && (ctx.minElementsStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.MIN_ELEMENT_DATA;
+            return false;
+        }
+
+        if ((!ctx.descriptionStatement().isEmpty())
+                && (ctx.descriptionStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.DESCRIPTION_DATA;
+            return false;
+        }
+
+        if ((!ctx.referenceStatement().isEmpty())
+                && (ctx.referenceStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.REFERENCE_DATA;
+            return false;
+        }
+
+        if ((!ctx.statusStatement().isEmpty())
+                && (ctx.statusStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = ParsableDataType.STATUS_DATA;
+            return false;
+        }
+
+        if (ctx.dataDefStatement().isEmpty()) {
+            yangConstruct = ParsableDataType.LIST_DATA;
+            return false;
+        }
+
+        return true;
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MandatoryListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MandatoryListener.java
index f062404..e0a3e6c 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MandatoryListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MandatoryListener.java
@@ -16,8 +16,16 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -57,18 +65,27 @@
      */
     public static void processMandatoryEntry(TreeWalkListener listener,
                                           GeneratedYangParser.MandatoryStatementContext ctx) {
-        // TODO method implementation
-    }
 
-    /**
-     * It is called when parser exits from grammar rule (mandatory), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processMandatoryExit(TreeWalkListener listener,
-                                         GeneratedYangParser.MandatoryStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.MANDATORY_DATA, "", ListenerErrorLocation.ENTRY);
+
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+            case LEAF_DATA:
+                YangLeaf leaf = (YangLeaf) tmpNode;
+                if (ctx.TRUE_KEYWORD() != null) {
+                    leaf.setMandatory(true);
+                } else {
+                    leaf.setMandatory(false);
+                }
+                break;
+            case CHOICE_DATA: // TODO
+                break;
+            default:
+                throw new ParserException(ListenerErrorMessageConstruction
+                        .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                ParsableDataType.MANDATORY_DATA, "", ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MaxElementsListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MaxElementsListener.java
index d0ba5fa..84eefea 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MaxElementsListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MaxElementsListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -54,18 +63,33 @@
      */
     public static void processMaxElementsEntry(TreeWalkListener listener,
                                              GeneratedYangParser.MaxElementsStatementContext ctx) {
-        // TODO method implementation
-    }
+        int maxElementsValue;
 
-    /**
-     * It is called when parser exits from grammar rule (max-elements), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processMaxElementsExit(TreeWalkListener listener,
-                                            GeneratedYangParser.MaxElementsStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.MAX_ELEMENT_DATA, "", ListenerErrorLocation.ENTRY);
+
+        if (ctx.maxValueArgument().UNBOUNDED_KEYWORD() != null) {
+            maxElementsValue = Integer.MAX_VALUE;
+        } else {
+            maxElementsValue = Integer.parseInt(ctx.maxValueArgument().INTEGER().getText());
+        }
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        switch (tmpData.getParsableDataType()) {
+            case LEAF_LIST_DATA:
+                YangLeafList leafList = (YangLeafList) tmpData;
+                leafList.setMaxElelements(maxElementsValue);
+                break;
+            case LIST_DATA:
+                YangList yangList = (YangList) tmpData;
+                yangList.setMaxElelements(maxElementsValue);
+                break;
+            default:
+                throw new ParserException(ListenerErrorMessageConstruction
+                        .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                ParsableDataType.MAX_ELEMENT_DATA,
+                                "", ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MinElementsListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MinElementsListener.java
index 0f18f90..87a9cdb 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MinElementsListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/MinElementsListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -55,18 +64,28 @@
      */
     public static void processMinElementsEntry(TreeWalkListener listener,
                                                GeneratedYangParser.MinElementsStatementContext ctx) {
-        // TODO method implementation
-    }
 
-    /**
-     * It is called when parser exits from grammar rule (min-elements), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processMinElementsExit(TreeWalkListener listener,
-                                              GeneratedYangParser.MinElementsStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.MIN_ELEMENT_DATA, String.valueOf(ctx.INTEGER().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        switch (tmpData.getParsableDataType()) {
+            case LEAF_LIST_DATA:
+                YangLeafList leafList = (YangLeafList) tmpData;
+                leafList.setMinElements(Integer.parseInt(ctx.INTEGER().getText()));
+                break;
+            case LIST_DATA:
+                YangList yangList = (YangList) tmpData;
+                yangList.setMinElements(Integer.parseInt(ctx.INTEGER().getText()));
+                break;
+            default:
+                throw new ParserException(ListenerErrorMessageConstruction
+                        .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                ParsableDataType.MIN_ELEMENT_DATA,
+                                String.valueOf(ctx.INTEGER().getText()),
+                                ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PresenceListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PresenceListener.java
index a4bfc67..b63f901 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PresenceListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PresenceListener.java
@@ -16,8 +16,16 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -51,18 +59,22 @@
      */
     public static void processPresenceEntry(TreeWalkListener listener,
                                              GeneratedYangParser.PresenceStatementContext ctx) {
-        // TODO method implementation
-    }
 
-    /**
-     * It is called when parser exits from grammar rule (presence), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processPresenceExit(TreeWalkListener listener,
-                                            GeneratedYangParser.PresenceStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.PRESENCE_DATA, String.valueOf(ctx.string().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        if (tmpData.getParsableDataType() == ParsableDataType.CONTAINER_DATA) {
+            YangContainer container = (YangContainer) tmpData;
+            container.setPresence(ctx.string().getText());
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.PRESENCE_DATA,
+                            String.valueOf(ctx.string().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ReferenceListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ReferenceListener.java
index cfe7576..2c6e0d0 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ReferenceListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ReferenceListener.java
@@ -16,8 +16,16 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangReference;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -51,18 +59,22 @@
      */
     public static void processReferenceEntry(TreeWalkListener listener,
                                              GeneratedYangParser.ReferenceStatementContext ctx) {
-        // TODO method implementation
-    }
 
-    /**
-     * It is called when parser exits from grammar rule (reference), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processReferenceExit(TreeWalkListener listener,
-                                            GeneratedYangParser.ReferenceStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.REFERENCE_DATA, String.valueOf(ctx.string().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        if (tmpData instanceof YangReference) {
+            YangReference reference = (YangReference) tmpData;
+            reference.setReference(ctx.string().getText());
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.REFERENCE_DATA,
+                            String.valueOf(ctx.string().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/StatusListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/StatusListener.java
index c30a7a8..c52f3e6 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/StatusListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/StatusListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangStatus;
+import org.onosproject.yangutils.datamodel.YangStatusType;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -56,18 +65,28 @@
      */
     public static void processStatusEntry(TreeWalkListener listener,
                                           GeneratedYangParser.StatusStatementContext ctx) {
-        // TODO method implementation
-    }
+        YangStatusType status;
 
-    /**
-     * It is called when parser exits from grammar rule (status), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processStatusExit(TreeWalkListener listener,
-                                              GeneratedYangParser.StatusStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.STATUS_DATA, "", ListenerErrorLocation.ENTRY);
+
+        if (ctx.CURRENT_KEYWORD() != null) {
+            status = YangStatusType.CURRENT.CURRENT;
+        } else if (ctx.DEPRECATED_KEYWORD() != null) {
+            status = YangStatusType.DEPRECATED;
+        } else {
+            status = YangStatusType.OBSOLETE.OBSOLETE;
+        }
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        if (tmpData instanceof YangStatus) {
+            YangStatus yangStatus = (YangStatus) tmpData;
+            yangStatus.setStatus(status);
+        } else {
+            throw new ParserException(ListenerErrorMessageConstruction
+                    .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.STATUS_DATA, "", ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
index 2488b4d..fffa86a 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
@@ -16,8 +16,19 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangDataTypes;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangType;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -55,18 +66,35 @@
      */
     public static void processTypeEntry(TreeWalkListener listener,
                                         GeneratedYangParser.TypeStatementContext ctx) {
-        // TODO method implementation
-    }
 
-    /**
-     * It is called when parser exits from grammar rule (type), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processTypeExit(TreeWalkListener listener,
-                                       GeneratedYangParser.TypeStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.TYPE_DATA, String.valueOf(ctx.string().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        YangType type = new YangType();
+        YangDataTypes yangDataTypes = YangDataTypes.getType(ctx.string().getText());
+        type.setDataTypeName(ctx.string().getText());
+        type.setDataType(yangDataTypes);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        switch (tmpData.getParsableDataType()) {
+            case LEAF_DATA:
+                YangLeaf leaf = (YangLeaf) tmpData;
+                leaf.setDataType(type);
+                break;
+            case LEAF_LIST_DATA:
+                YangLeafList leafList = (YangLeafList) tmpData;
+                leafList.setDataType(type);
+                break;
+            case TYPEDEF_DATA: //TODO
+                break;
+            default:
+                throw new ParserException(ListenerErrorMessageConstruction
+                        .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                ParsableDataType.TYPE_DATA,
+                                String.valueOf(ctx.string().getText()),
+                                ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/UnitsListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/UnitsListener.java
index 59c44a0..e846b42 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/UnitsListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/UnitsListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -51,18 +60,31 @@
      */
     public static void processUnitsEntry(TreeWalkListener listener,
                                            GeneratedYangParser.UnitsStatementContext ctx) {
-        // TODO method implementation
-    }
 
-    /**
-     * It is called when parser exits from grammar rule (units), it performs
-     * validation and updates the data model tree.
-     *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processUnitsExit(TreeWalkListener listener,
-                                          GeneratedYangParser.UnitsStatementContext ctx) {
-        // TODO method implementation
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                ParsableDataType.UNITS_DATA, String.valueOf(ctx.string().getText()),
+                ListenerErrorLocation.ENTRY);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        switch (tmpData.getParsableDataType()) {
+            case LEAF_DATA:
+                YangLeaf leaf = (YangLeaf) tmpData;
+                leaf.setUnits(ctx.string().getText());
+                break;
+            case LEAF_LIST_DATA:
+                YangLeafList leafList = (YangLeafList) tmpData;
+                leafList.setUnits(ctx.string().getText());
+                break;
+            case TYPEDEF_DATA:
+                // TODO
+                break;
+            default:
+                throw new ParserException(ListenerErrorMessageConstruction
+                        .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                ParsableDataType.UNITS_DATA,
+                                String.valueOf(ctx.string().getText()),
+                                ListenerErrorLocation.ENTRY));
+        }
     }
 }
\ No newline at end of file