/*
 * 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.Nullable;

/**
 * @author peter
 */
public abstract class NullableLazyValue<T> {
  private static final RecursionGuard ourGuard = RecursionManager.createGuard("NullableLazyValue");
  private boolean myComputed;
  @Nullable private T myValue;

  @Nullable
  protected abstract T compute();

  @Nullable
  public T getValue() {
    T value = myValue;
    if (!myComputed) {
      RecursionGuard.StackStamp stamp = ourGuard.markStack();
      value = compute();
      if (stamp.mayCacheNow()) {
        myValue = value;
        myComputed = true;
      }
    }
    return value;
  }
}

@@ -20,10 +20,10 @@
 0-20
-09
+16
  Jet
@@ -630,16 +630,58 @@
 .util;%0A%0A
+import org.jetbrains.annotations.NotNull;%0A
 import o
@@ -1259,24 +1259,24 @@
     %7D%0A    %7D%0A
-
     return v
@@ -1284,11 +1284,264 @@
 lue;%0A  %7D
+%0A%0A  @NotNull%0A  public static %3CT%3E NullableLazyValue%3CT%3E createValue(@NotNull final Factory%3CT%3E value) %7B%0A    return new NullableLazyValue%3CT%3E() %7B%0A%0A      @Nullable%0A      @Override%0A      protected T compute() %7B%0A        return value.create();%0A      %7D%0A    %7D;%0A  %7D
 %0A%7D%0A

add lambda-friendly factory method for NullableLazyValue