java 锁实例

1.Lock的简单应用

public class LockTest {
	public static void main(String[] args) {
		final Outputter1 output = new Outputter1();
		new Thread() {
			public void run() {
				output.output("zhangsan");
			};
		}.start();		
		new Thread() {
			public void run() {
				output.output("lisi");
			};
		}.start();
	}
}
class Outputter1 {
	private Lock lock = new ReentrantLock();// 锁对象
	public void output(String name) {
		// TODO 线程输出方法
		lock.lock();// 得到锁
		try {
			for(int i = 0; i < name.length(); i++) {
				System.out.print(name.charAt(i));
			}
		} finally {
			lock.unlock();// 释放锁
		}
	}
}

2.Condition的应用

public class ConditionTest {
	public static void main(String[] args) {
		final Business business = new Business();
		new Thread(new Runnable() {
			@Override
			public void run() {
				threadExecute(business, "sub");
			}
		}).start();
		threadExecute(business, "main");
	}

	public static void threadExecute(Business business, String threadType) {
		for (int i = 0; i < 10; i++) {
			try {
				if ("main".equals(threadType)) {
					business.main(i);
				} else {
					business.sub(i);
				}
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
}

class Business {
	private boolean bool = true;
	private Lock lock = new ReentrantLock();
	private Condition condition = lock.newCondition();

	public/* synchronized */void main(int loop) throws InterruptedException {
		lock.lock();
		try {
			while (bool) {
				condition.await();// this.wait();
			}
			for (int i = 0; i < 10; i++) {
				System.out.println("main thread seq of " + i + ", loop of "
						+ loop);
			}
			bool = true;
			condition.signal();// this.notify();
		} finally {
			lock.unlock();
		}
	}

	public/* synchronized */void sub(int loop) throws InterruptedException {
		lock.lock();
		try {
			while (!bool) {
				condition.await();// this.wait();
			}
			for (int i = 0; i < 10; i++) {
				System.out.println("sub thread seq of " + i + ", loop of "
						+ loop);
			}
			bool = false;
			condition.signal();// this.notify();
		} finally {
			lock.unlock();
		}
	}
}

3.读写锁ReadWriteLock

public class ReadWriteLockTest {
	public static void main(String[] args) {
		final Data data = new Data();
		for (int i = 0; i < 3; i++) {
			new Thread(new Runnable() {
				public void run() {
					for (int j = 0; j < 5; j++) {
						data.set(new Random().nextInt(30));
					}
				}
			}).start();
		}
		for (int i = 0; i < 3; i++) {
			new Thread(new Runnable() {
				public void run() {
					for (int j = 0; j < 5; j++) {
						data.get();
					}
				}
			}).start();
		}
	}
}

class Data {	
	private int data;// 共享数据
	private ReadWriteLock rwl = new ReentrantReadWriteLock();	
	public void set(int data) {
		rwl.writeLock().lock();// 取到写锁
		try {
			System.out.println(Thread.currentThread().getName() + "准备写入数据");
			try {
				Thread.sleep(20);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			this.data = data;
			System.out.println(Thread.currentThread().getName() + "写入" + this.data);
		} finally {
			rwl.writeLock().unlock();// 释放写锁
			try {
				Thread.sleep(2);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}	
	public void get() {
		rwl.readLock().lock();// 取到读锁
		try {
			System.out.println(Thread.currentThread().getName() + "准备读取数据");
			try {
				Thread.sleep(20);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			System.out.println(Thread.currentThread().getName() + "读取" + this.data);
		} finally {
			rwl.readLock().unlock();// 释放读锁
		}
	}
}

4.环形缓存区简单实现

public class BoundedBuffer {
	final Lock lock = new ReentrantLock();// 锁对象
	final Condition notFull = lock.newCondition();// 写线程条件
	final Condition notEmpty = lock.newCondition();// 读线程条件

	final Object[] items = new Object[100];// 缓存队列
	int putptr/* 写索引 */, takeptr/* 读索引 */, count/* 队列中存在的数据个数 */;

	public void put(Object x) throws InterruptedException {
		lock.lock();
		try {
			while (count == items.length) {
				// 如果队列满了
				notFull.await();// 阻塞写线程
			}
			items[putptr] = x;// 赋值
			if (++putptr == items.length) {
				putptr = 0;// 如果写索引写到队列的最后一个位置了，那么置为0
			}
			++count;// 个数++
			notEmpty.signal();// 唤醒读线程
		} finally {
			lock.unlock();
		}
	}

	public Object take() throws InterruptedException {
		lock.lock();
		try {
			while (count == 0) {
				// 如果队列为空
				notEmpty.await();// 阻塞读线程
			}
			Object x = items[takeptr];// 取值
			if (++takeptr == items.length) {
				takeptr = 0;// 如果读索引读到队列的最后一个位置了，那么置为0
			}
			--count;// 个数--
			notFull.signal();// 唤醒写线程
			return x;
		} finally {
			lock.unlock();
		}
	}
}