| /* |
| * Copyright 2000-2012 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.NotNull; |
| |
| /** |
| * Compute-once keep-forever lazy value. |
| * Thread-safe version: {@link AtomicNotNullLazyValue}. |
| * Clearable version: {@link ClearableLazyValue}. |
| * |
| * @author peter |
| */ |
| public abstract class NotNullLazyValue<T> { |
| private T myValue; |
| |
| @NotNull |
| protected abstract T compute(); |
| |
| @NotNull |
| public T getValue() { |
| if (myValue == null) { |
| myValue = compute(); |
| } |
| return myValue; |
| } |
| |
| @NotNull |
| public static <T> NotNullLazyValue<T> createConstantValue(@NotNull final T value) { |
| return new NotNullLazyValue<T>() { |
| @NotNull |
| @Override |
| protected T compute() { |
| return value; |
| } |
| }; |
| } |
| } |