org.apache.hudi.util.Lazy Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.hudi.util;
import javax.annotation.concurrent.ThreadSafe;
import java.util.function.Supplier;
/**
* Utility implementing lazy semantics in Java
*
* @param type of the object being held by {@link Lazy}
*/
@ThreadSafe
public class Lazy {
private volatile boolean initialized;
private Supplier initializer;
private T ref;
private Lazy(Supplier initializer) {
this.initializer = initializer;
this.ref = null;
this.initialized = false;
}
private Lazy(T ref) {
this.initializer = null;
this.ref = ref;
this.initialized = true;
}
public T get() {
if (!initialized) {
synchronized (this) {
if (!initialized) {
this.ref = initializer.get();
this.initializer = null;
initialized = true;
}
}
}
return ref;
}
/**
* Executes provided {@code initializer} lazily, while providing for "exactly once" semantic,
* to instantiate value of type {@link T} being subsequently held by the returned instance of
* {@link Lazy}
*/
public static Lazy lazily(Supplier initializer) {
return new Lazy<>(initializer);
}
/**
* Instantiates {@link Lazy} in an "eagerly" fashion setting it w/ the provided value of
* type {@link T} directly, bypassing lazy initialization sequence
*/
public static Lazy eagerly(T ref) {
return new Lazy<>(ref);
}
}