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/*
* 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;
}
};
}
}
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