src/share/classes/java/lang/StringBuffer.java

@@ -555,10 +555,40 @@
     public synchronized StringBuffer reverse() {
         super.reverse();
         return this;
     }
 
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @since 1.7
+     */
+    @Override
+    public synchronized StringBuffer join(String delimiter, Object first, Object... elements) {
+        super.join(delimiter, first, elements);
+        return this;
+    }
+    
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @since 1.7
+     */
+    @Override
+    public synchronized StringBuffer join(String delimiter, Object[] elements) {
+        super.join(delimiter, elements);
+        return this;
+    }
+    
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @since 1.7
+     */
+    @Override
+    public synchronized StringBuffer join(String delimiter, Iterable<?> elements) {
+        super.join(delimiter, elements);
+        return this;
+    }
+    
     public synchronized String toString() {
         return new String(value, 0, count);
     }
 
     /**