/*
 * 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;

import org.jetbrains.annotations.NonNls;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

/**
 * @author max
 * @author Konstantin Bulenkov
 */
@SuppressWarnings({"AssignmentToStaticFieldFromInstanceMethod", "UnusedDeclaration", "EqualsWhichDoesntCheckParameterClass"})
public class Key<T> {
  private static int ourKeysCounter = 0;
  private final int myIndex = ourKeysCounter++;

  private final String myName; // for debug purposes only

  public Key(@NotNull @NonNls String name) {
    myName = name;
  }

  public int hashCode() {
    return myIndex;
  }

  @Override
  public boolean equals(Object obj) {
    return obj == this;
  }

  public String toString() {
    return myName;
  }

  public static <T> Key<T> create(@NotNull @NonNls String name) {
    return new Key<T>(name);
  }

  @Nullable
  public T get(@Nullable UserDataHolder holder) {
    return holder == null ? null : holder.getUserData(this);
  }

  public T get(@Nullable UserDataHolder holder, T defaultValue) {
    final T t = get(holder);
    return t == null ? defaultValue : t;
  }

  /**
   * Returns <code>true</code> if and only if the <code>holder</code> has
   * not null value by the key.
   *
   * @param holder user data holder object
   * @return <code>true</code> if holder.getUserData(this) != null
   * <code>false</code> otherwise.
   */
  public boolean isIn(@Nullable UserDataHolder holder) {
    return get(holder) != null;
  }

  public void set(@Nullable UserDataHolder holder, T value) {
    if (holder != null) {
      holder.putUserData(this, value);
    }
  }
}
@@ -757,16 +757,39 @@
 lable;%0A%0A
+import java.util.Map;%0A%0A
 /**%0A * @
@@ -1607,24 +1607,149 @@
 this);%0A  %7D%0A%0A
+  @Nullable%0A  public T get(@Nullable Map%3CKey, Object%3E holder) %7B%0A    return holder == null ? null : (T)holder.get(this);%0A  %7D%0A%0A
   public T g
@@ -2323,24 +2323,24 @@
  != null) %7B%0A
-
       holder
@@ -2375,10 +2375,142 @@
    %7D%0A  %7D
+%0A%0A  public void set(@Nullable Map%3CKey, Object%3E holder, T value) %7B%0A    if (holder != null) %7B%0A      holder.put(this, value);%0A    %7D%0A  %7D
 %0A%7D

allow key to get / set values to map