Replace calls to String.isEmpty by a .length() == 0, as the isEmpty method is only available in the JDK 7.

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1592835 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/ipojo/runtime/core/src/main/java/org/apache/felix/ipojo/configuration/Instance.java b/ipojo/runtime/core/src/main/java/org/apache/felix/ipojo/configuration/Instance.java
index 93f1f3d..3dd0794 100644
--- a/ipojo/runtime/core/src/main/java/org/apache/felix/ipojo/configuration/Instance.java
+++ b/ipojo/runtime/core/src/main/java/org/apache/felix/ipojo/configuration/Instance.java
@@ -86,7 +86,7 @@
     }
 
     public Instance named(String name) {
-        if (name == null || name.isEmpty()) {
+        if (name == null || name.length() == 0) {
             throw new IllegalArgumentException("The instance name cannot be null or empty");
         }
         this.name = name;
@@ -166,7 +166,7 @@
         private T value;
 
         Property(String name) {
-            if (name == null || name.isEmpty()) {
+            if (name == null || name.length() == 0) {
                 throw new IllegalArgumentException("The property name cannot be null or empty");
             }
             this.name = name;
@@ -174,7 +174,7 @@
 
         public Instance setto(T value) {
             if ("instance.name".endsWith(name)) {
-                if (value == null || value.toString().isEmpty()) {
+                if (value == null || value.toString().length() == 0) {
                     throw new IllegalArgumentException("The instance name cannot be null or empty");
                 }
             }