com.datastax.oss.driver.internal.core.util.concurrent.LazyReference Maven / Gradle / Ivy
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/*
* 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 com.datastax.oss.driver.internal.core.util.concurrent;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Supplier;
import net.jcip.annotations.ThreadSafe;
/** Holds a reference to an object that is initialized on first access. */
@ThreadSafe
public class LazyReference {
private final String name;
private final Supplier supplier;
private final CycleDetector checker;
private volatile T value;
private final ReentrantLock lock = new ReentrantLock();
public LazyReference(String name, Supplier supplier, CycleDetector cycleDetector) {
this.name = name;
this.supplier = supplier;
this.checker = cycleDetector;
}
public LazyReference(Supplier supplier) {
this(null, supplier, null);
}
public T get() {
T t = value;
if (t == null) {
if (checker != null) {
checker.onTryLock(this);
}
lock.lock();
try {
if (checker != null) {
checker.onLockAcquired(this);
}
t = value;
if (t == null) {
value = t = supplier.get();
}
} finally {
if (checker != null) {
checker.onReleaseLock(this);
}
lock.unlock();
}
}
return t;
}
public String getName() {
return name;
}
}