src/java.desktop/macosx/native/libawt_lwawt/awt/AWTWindow.m

@@ -883,22 +883,30 @@
 
             NSPoint p = [NSEvent mouseLocation];
             NSRect frame = [self.nsWindow frame];
             NSRect contentRect = [self.nsWindow contentRectForFrameRect:frame];
 
-            // Check if the click happened in the non-client area (title bar)
-            if (p.y >= (frame.origin.y + contentRect.size.height)) {
                 JNIEnv *env = [ThreadUtilities getJNIEnvUncached];
                 jobject platformWindow = [self.javaPlatformWindow jObjectWithEnv:env];
+            
+            // Check if the click happened in the non-client area (title bar)
+            if (p.y >= (frame.origin.y + contentRect.size.height)) {
                 if (platformWindow != NULL) {
+                    // Toggle full screen upon double click on title bar.
+                    if([event clickCount] == 2) {
+                        static JNF_MEMBER_CACHE(jm_deliverNCDblClick, jc_CPlatformWindow, "deliverNCDblClick", "()V");
+                        JNFCallVoidMethod(env, platformWindow, jm_deliverNCDblClick);
+                    } else {
                     // Currently, no need to deliver the whole NSEvent.
                     static JNF_MEMBER_CACHE(jm_deliverNCMouseDown, jc_CPlatformWindow, "deliverNCMouseDown", "()V");
                     JNFCallVoidMethod(env, platformWindow, jm_deliverNCMouseDown);
-                    (*env)->DeleteLocalRef(env, platformWindow);
                 }
             }
         }
+            
+            (*env)->DeleteLocalRef(env, platformWindow);
+        }
 }
 
 - (void)constrainSize:(NSSize*)size {
     float minWidth = 0.f, minHeight = 0.f;