io.cdap.plugin.util.Lazy Maven / Gradle / Ivy
/*
* Copyright © 2019 Cask Data, Inc.
*
* 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 io.cdap.plugin.util;
import java.util.function.Supplier;
import static java.util.Objects.requireNonNull;
/**
* Helper class for lazy field initialization. Implementation is thread-safe.
*
* @param value type
*/
public final class Lazy {
private final Supplier supplier;
private volatile T value;
public Lazy(Supplier supplier) {
this.supplier = supplier;
}
public T getOrCompute() {
final T result = value; // Just one volatile read
return result == null ? compute() : result;
}
private synchronized T compute() {
if (value == null) {
value = requireNonNull(supplier.get());
}
return value;
}
}