// Copyright (C) 2012 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.gerrit.client.ui;

public class ListenableOldValue<T> extends ListenableValue<T> {

  private T oldValue;

  public T getOld() {
    return oldValue;
  }

  public void set(final T value) {
    oldValue = get();
    super.set(value);
    oldValue = null; // allow it to be gced before the next event
  }
}

@@ -807,24 +807,36 @@
  T value) %7B%0A
+    try %7B%0A  
     oldValue
@@ -845,16 +845,18 @@
  get();%0A
+  
     supe
@@ -869,16 +869,34 @@
 value);%0A
+    %7D finally %7B%0A  
     oldV
@@ -953,14 +953,20 @@
 t event%0A
+    %7D%0A
   %7D%0A%7D%0A

Use try/finally to ensure oldValue is cleared