Add missing Javadoc

Change-Id: I7aa4a34831ad26a157b3616cc89cca42e5bfae7e
diff --git a/src/main/java/net/onrc/onos/core/newintent/IdBlockAllocatorBasedIntentIdGenerator.java b/src/main/java/net/onrc/onos/core/newintent/IdBlockAllocatorBasedIntentIdGenerator.java
index 2099697..29f14a1 100644
--- a/src/main/java/net/onrc/onos/core/newintent/IdBlockAllocatorBasedIntentIdGenerator.java
+++ b/src/main/java/net/onrc/onos/core/newintent/IdBlockAllocatorBasedIntentIdGenerator.java
@@ -17,6 +17,11 @@
     private final IdBlockAllocator allocator;
     private IdBlock idBlock;
 
+    /**
+     * Constructs a {@link IdBlockAllocatorBasedIntentIdGenerator}.
+     *
+     * @param allocator ID block allocator, which is used in this class
+     */
     public IdBlockAllocatorBasedIntentIdGenerator(IdBlockAllocator allocator) {
         this.allocator = checkNotNull(allocator);
         this.idBlock = allocator.allocateUniqueIdBlock();