java多线程编程——显示锁ReentrantLock（一）
package test;
/**
* 内部锁
*
* @author Administrator
*
*/
public class SynchronizedBenchmarkDemo implements Counter {
private long count = 0;
@Override
public long getValue() {
return count;
}
@Override
public synchronized void increment() {
count++;
}
}
package test;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 不公平重入锁
*
* @author Administrator
*
*/
@SuppressWarnings("all")
public class ReentrantLockUnfairBeanchmarkDemo implements Counter {
private volatile long count = 0;
private Lock lock;
public ReentrantLockUnfairBeanchmarkDemo() {
// 使用不公平锁
lock = new ReentrantLock(false);
}
@Override
public long getValue() {
return count;
}
@Override
public void increment() {
lock.lock();
try {
count++;
} finally {
lock.unlock();
}
}
}
package test;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 公平重入锁
*
* @author Administrator
*
*/
@SuppressWarnings("all")
public class ReentrantLockFairBeanchmarkDemo implements Counter {
private volatile long count = 0;
private Lock lock;
public ReentrantLockFairBeanchmarkDemo() {
// 创建公平锁
lock = new ReentrantLock(true);
}
@Override
public long getValue() {
return count;
}
@Override
public void increment() {
lock.lock();
try {
count++;
} finally {
lock.unlock();
}
}
}
package test;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
/**
* 三种类型的同步锁：内部锁、不公平锁、公平锁，每种类型的锁各自创建2000个线程，然后每个线程访问带有锁得变量100次，并加1。
* 统计各种锁并发访问时消耗的时间
*
* @author Administrator
*
*/
@SuppressWarnings("all")
public class BenchmarkTest {
private Counter counter;
// 一个同步辅助类，它允许一组线程互相等待，直到到达某个公共屏障点
private CyclicBarrier barrier;
private int threadNum;
private int loopNum;
private String testName;
/*******************************************************************
* 用于记录由该对象创建的threadNum线程统开始循环和结束循环的起止时间
*/
public long begin;
public long end;
private BenchmarkTest(Counter counter, int threadNum, int loopNum, String testName) {
this.counter = counter;
this.threadNum = threadNum;
this.loopNum = loopNum;
this.testName = testName;
barrier = new CyclicBarrier(threadNum, new BarrierTime(this));
}
public void test() {
try {
for (int i = 0; i < threadNum; i++) {
new TestThread(counter, loopNum, this).start();
}
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
try {
int threadNum = 2000;
int loopNum = 100;
new BenchmarkTest(new SynchronizedBenchmarkDemo(), threadNum, loopNum, "内部锁").test();
Thread.sleep(5000);
new BenchmarkTest(new ReentrantLockUnfairBeanchmarkDemo(), threadNum, loopNum, "不公平锁").test();
Thread.sleep(5000);
new BenchmarkTest(new ReentrantLockFairBeanchmarkDemo(), threadNum, loopNum, "公平锁锁").test();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
class TestThread extends Thread {
int loopNum = 100;
private Counter counter;
private BenchmarkTest benchmarkTest;
private TestThread(final Counter counter, int loopNum, BenchmarkTest benchmarkTest) {
this.counter = counter;
this.loopNum = loopNum;
this.benchmarkTest = benchmarkTest;
}
public void run() {
try {
// 等待所有线程开始
barrier.await();
for (int i = 0; i < this.loopNum; i++) {
counter.increment();
}
// 等待所有线程结束
barrier.await();
} catch (Exception e) {
throw new RuntimeException();
}
}
}
class BarrierTime implements Runnable {
private BenchmarkTest benchmarkTest;
public BarrierTime(BenchmarkTest benchmarkTest) {
this.benchmarkTest = benchmarkTest;
}
@Override
public void run() {
if (benchmarkTest.begin == 0) {
benchmarkTest.begin = System.currentTimeMillis();
} else {
benchmarkTest.end = System.currentTimeMillis();
}
if (benchmarkTest.end != 0) {
System.out.println(benchmarkTest.testName + "共花费时间：" + (benchmarkTest.end - benchmarkTest.begin) + "毫秒");
}
}
}
}
内部锁共花费时间：260毫秒
不公平锁共花费时间：26毫秒
公平锁锁共花费时间：1471毫秒