Added JsonObject method isEmpty() (google#2233)

* Added isEmpty()

* Fixed Javadoc typo

* Changed test to use assertTrue() and assertFalse()

(cherry picked from commit ceb3b87)

gson/src/main/java/com/google/gson/JsonObject.java

@@ -155,6 +155,16 @@ public int size() {
     return members.size();
   }
 
+  /**
+   * Returns true if the number of key/value pairs in the object is zero.
+   *
+   * @return true if the number of key/value pairs in the object is zero.
+   * @since $next-version$
+   */
+  public boolean isEmpty() {
+    return members.size() == 0;
+  }
+
   /**
    * Convenience method to check if a member with the specified name is present in this object.
    *

gson/src/test/java/com/google/gson/JsonObjectTest.java

@@ -222,6 +222,18 @@ public void testSize() {
     assertEquals(1, o.size());
   }
 
+  @Test
+  public void testIsEmpty() {
+    JsonObject o = new JsonObject();
+    assertTrue(o.isEmpty());
+
+    o.add("Hello", new JsonPrimitive(1));
+    assertFalse(o.isEmpty());
+
+    o.remove("Hello");
+    assertTrue(o.isEmpty());
+  }
+
   @Test
   public void testDeepCopy() {
     JsonObject original = new JsonObject();