platform/core-api/src/com/intellij/openapi/util/ModificationTracker.java

/*
 * Copyright 2000-2009 JetBrains s.r.o.
 *
 * 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.intellij.openapi.util;

/**
 * @author dyoma
 */
public interface ModificationTracker {
  long getModificationCount();

  ModificationTracker EVER_CHANGED = new ModificationTracker() {
    private long myCounter = 0;

    @Override
    public long getModificationCount() {
      return myCounter++;
    }
  };
  ModificationTracker NEVER_CHANGED = new ModificationTracker() {
    @Override
    public long getModificationCount() {
      return 0;
    }
  };
}