import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class AReentrantReadWriteLock {
static ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
public static void main(String[] args) throws InterruptedException {
// deadLock();
// releaseLock();
// upGradLock();
// downGrad();
// testSync();
// testRWL();
// readWriteSameTime();
// writeWriteSameTime();
readReadSameTime();
}
/**
* 同时读测试
*/
public static void readReadSameTime(){
ExecutorService service= Executors.newCachedThreadPool();
service.execute(new Runnable() {
@Override
public void run() {
readFile(Thread.currentThread());
}
});
service.execute(new Runnable() {
@Override
public void run() {
readFile(Thread.currentThread());
}
});
}
/**
* 同时写测试
*/
public static void writeWriteSameTime(){
ExecutorService service= Executors.newCachedThreadPool();
service.execute(new Runnable() {
@Override
public void run() {
writeFile(Thread.currentThread());
}
});
service.execute(new Runnable() {
@Override
public void run() {
writeFile(Thread.currentThread());
}
});
}
/**
* 同时读写测试
*/
public static void readWriteSameTime(){
ExecutorService service= Executors.newCachedThreadPool();
service.execute(new Runnable() {
@Override
public void run() {
writeFile(Thread.currentThread());
}
});
service.execute(new Runnable() {
@Override
public void run() {
readFile(Thread.currentThread());
}
});
}
// 读操作
public static void readFile(Thread thread) {
lock.readLock().lock();
boolean readLock = lock.isWriteLocked();
if (!readLock) {
System.out.println("当前为读锁！");
}
try {
for (int i = 0; i < 5; i++) {
try {
Thread.sleep(20);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(thread.getName() + ":正在进行读操作……");
}
System.out.println(thread.getName() + ":读操作完毕！");
} finally {
System.out.println("释放读锁！");
lock.readLock().unlock();
}
}
// 写操作
public static void writeFile(Thread thread) {
lock.writeLock().lock();
boolean writeLock = lock.isWriteLocked();
if (writeLock) {
System.out.println("当前为写锁！");
}
try {
for (int i = 0; i < 5; i++) {
try {
Thread.sleep(20);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(thread.getName() + ":正在进行写操作……");
}
System.out.println(thread.getName() + ":写操作完毕！");
} finally {
System.out.println("释放写锁！");
lock.writeLock().unlock();
}
}
/**
* 测试读写锁同时执行
*/
public static void testRWL(){
new Thread(new Runnable() {
@Override
public void run() {
getRWL(Thread.currentThread());
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
getRWL(Thread.currentThread());
}
}).start();
}
/**
* ReentrantReadWriteLock
* @param thread
*/
public static void getRWL(Thread thread) {
lock.readLock().lock();
System.out.println("start time:" + System.currentTimeMillis());
for (int i = 0; i < 5; i++) {
try {
Thread.sleep(20);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(thread.getName() + ":正在进行读操作……");
}
System.out.println(thread.getName() + ":读操作完毕！");
System.out.println("end time:" + System.currentTimeMillis());
lock.readLock().unlock();
}
public static void testSync(){
new Thread(new Runnable() {
@Override
public void run() {
getSync(Thread.currentThread());
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
getSync(Thread.currentThread());
}
}).start();
}
/**
* synchronized实现读写锁
* @param thread
*/
public synchronized static void getSync(Thread thread) {
System.out.println("start time:" + System.currentTimeMillis());
for (int i = 0; i < 5; i++) {
try {
Thread.sleep(20);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(thread.getName() + ":正在进行读操作……");
}
System.out.println(thread.getName() + ":读操作完毕！");
System.out.println("end time:" + System.currentTimeMillis());
}
/**
* 锁降级
* ReentrantReadWriteLock支持锁降级
*/
public static void downGrad(){
ReentrantReadWriteLock rtLock = new ReentrantReadWriteLock();
rtLock.writeLock().lock();
System.out.println("writeLock");
rtLock.readLock().lock();
System.out.println("get read lock");
}
/**
* 锁升级
* ReentrantReadWriteLock不支持锁升级
*/
public static void upGradLock(){
ReentrantReadWriteLock rtLock = new ReentrantReadWriteLock();
rtLock.readLock().lock();
System.out.println("get readLock.");
rtLock.writeLock().lock();
System.out.println("blocking");
}
/**
* 死锁
* 获得几次锁,就要释放几次锁
* @throws InterruptedException
*/
public static void deadLock() throws InterruptedException {
Thread t = new Thread(new Runnable() {
@Override
public void run() {
lock.writeLock().lock();
System.out.println("Thread real execute");
lock.writeLock().unlock();
}
});
lock.writeLock().lock();
lock.writeLock().lock();
t.start();
Thread.sleep(200);
System.out.println("realse one once");
lock.writeLock().unlock();
}
/**
* 解锁
* 获得几次锁,就要释放几次锁
* @throws InterruptedException
*/
public static void releaseLock() throws InterruptedException {
Thread t = new Thread(new Runnable() {
@Override
public void run() {
lock.writeLock().lock();
System.out.println("Thread real execute");
lock.writeLock().unlock();
}
});
lock.writeLock().lock();
lock.writeLock().lock();
t.start();
Thread.sleep(200);
System.out.println("realse one once");
lock.writeLock().unlock();
lock.writeLock().unlock();
}
}
