JDK 5.0 Concurrency Utilities 并发处理（3）ReadWriteLock 读写锁

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package com.vinko.test.concurrent;

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import java.util.Calendar;

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import java.util.Map;

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import java.util.TreeMap;

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//import java.util.concurrent.locks.Condition;

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import java.util.concurrent.locks.Lock;

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import java.util.concurrent.locks.ReentrantReadWriteLock;

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public class TestReadWriteLock {

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private ReentrantReadWriteLock lock = null;

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private Lock readLock = null;

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private Lock writeLock = null;

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// private Condition condition = null;

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public int key = 100;

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public int index = 100;

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public Map<Integer, String> dataMap = null;

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public TestReadWriteLock() {

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lock = new ReentrantReadWriteLock(true);

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readLock = lock.readLock();

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writeLock = lock.writeLock();

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// condition = writeLock.newCondition();

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dataMap = new TreeMap<Integer, String>();

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}

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/**

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* @param args

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*/

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public static void main(String[] args) {

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TestReadWriteLock tester = new TestReadWriteLock();

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// test lock downgrading

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// tester.readLock.lock();

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// System.out.println(Thread.currentThread() + " get readLock");

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tester.writeLock.lock();

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System.out.println(Thread.currentThread() + " get writeLock.");

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tester.writeLock.lock();

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System.out.println(Thread.currentThread() + " get writeLock.");

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tester.readLock.lock();

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System.out.println(Thread.currentThread() + " get readLock");

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tester.readLock.lock();

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System.out.println(Thread.currentThread() + " get readLock");

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// tester.writeLock.lock();

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// System.out.println(Thread.currentThread() + " get writeLock.");

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tester.readLock.unlock();

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tester.readLock.unlock();

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tester.writeLock.unlock();

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tester.writeLock.unlock();

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tester.test();

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}

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public void test() {

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for (int i = 0; i < 10; i++) {

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new Thread(new reader(this)).start();

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}

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for (int i = 0; i <3; i++) {

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new Thread(new writer(this)).start();

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}

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}

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public void read() {

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/*

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writeLock.lock();

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try {

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condition.await();

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} catch (InterruptedException e1) {

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e1.printStackTrace();

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}

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writeLock.unlock();

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*/

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readLock.lock();

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try {

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if (dataMap.isEmpty()) {

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Calendar now = Calendar.getInstance();

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System.out.println(now.getTime() + " R " + Thread.currentThread() + " get key, but map is empty.");

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}

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String value = dataMap.get(index);

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Calendar now = Calendar.getInstance();

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System.out.println(now.getTime() + " R " + Thread.currentThread() + " get key = " + index + " value = " + value + " map size = " + dataMap.size());

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// get next value

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if (value != null) {

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index ++;

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}

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} finally {

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readLock.unlock();

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}

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try {

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Thread.sleep(3000);

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} catch (InterruptedException e) {

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e.printStackTrace();

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}

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}

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public void write() {

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writeLock.lock();

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try {

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String value = "value" + key;

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dataMap.put(new Integer(key), value);

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Calendar now = Calendar.getInstance();

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System.out.println(now.getTime() + " W " + Thread.currentThread() + " put key = " + key + " value = " + value + " map size = " + dataMap.size());

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key ++;

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// condition.signal();

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try {

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Thread.sleep(500);

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} catch (InterruptedException e) {

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e.printStackTrace();

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}

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} finally {

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writeLock.unlock();

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}

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}

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}

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class reader implements Runnable {

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private TestReadWriteLock tester = null;

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public reader(TestReadWriteLock tester) {

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this.tester = tester;

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}

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public void run() {

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Calendar now = Calendar.getInstance();

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System.out.println(now.getTime() + " R " + Thread.currentThread() + " started");

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while (true) {

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tester.read();

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}

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}

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}

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class writer implements Runnable {

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private TestReadWriteLock tester = null;

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public writer(TestReadWriteLock tester) {

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this.tester = tester;

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}

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public void run() {

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Calendar now = Calendar.getInstance();

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System.out.println(now.getTime() + " W " + Thread.currentThread() + " started");

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while (true) {

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tester.write();

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}

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}

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}