package seventeen;

//死锁的问题：处理线程同步时容易出现。
//不同的线程分别占用对方需要的同步资源不放弃，都在等待对方放弃自己需要的同步资源，就形成了线程的死锁
//写代码时，要避免死锁！
public class TestDeadLock {
	static StringBuffer sb1 = new StringBuffer();
	static StringBuffer sb2 = new StringBuffer();

	public static void main(String[] args) {
		new Thread() {
			public void run() {
				synchronized (sb1) {
					try {
//						Thread.currentThread().sleep(10);
						Thread.sleep(10);
					} catch (InterruptedException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
					sb1.append("A");
					synchronized (sb2) {
						sb2.append("B");
						System.out.println(sb1);
						System.out.println(sb2);
					}
				}
			}
		}.start();

		new Thread() {
			public void run() {
				synchronized (sb2) {
					try {
//						Thread.currentThread().sleep(10);
						Thread.sleep(10);
					} catch (InterruptedException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
					sb1.append("C");
					synchronized (sb1) {
						sb2.append("D");
						System.out.println(sb1);
						System.out.println(sb2);
					}
				}
			}
		}.start();
	}

}

package seventeen;

class A {
	public synchronized void foo(B b) {//锁：A 的对象 a
		System.out.println("当前线程名: " + Thread.currentThread().getName()
				+ " 进入了A实例的foo方法"); // ①
		try {
			Thread.sleep(200);
		} catch (InterruptedException ex) {
			ex.printStackTrace();
		}
		System.out.println("当前线程名: " + Thread.currentThread().getName()
				+ " 企图调用B实例的last方法"); // ③
		b.last();
	}

	public synchronized void last() {//锁：A 的对象 a
		System.out.println("进入了A类的last方法内部");
	}
}

class B {
	public synchronized void bar(A a) {//锁：B 的对象 b
		System.out.println("当前线程名: " + Thread.currentThread().getName()
				+ " 进入了B实例的bar方法"); // ②
		try {
			Thread.sleep(200);
		} catch (InterruptedException ex) {
			ex.printStackTrace();
		}
		System.out.println("当前线程名: " + Thread.currentThread().getName()
				+ " 企图调用A实例的last方法"); // ④
		a.last();
	}

	public synchronized void last() {//锁：B 的对象 b
		System.out.println("进入了B类的last方法内部");
	}
}

public class DeadLock implements Runnable {
	A a = new A();
	B b = new B();

	public void init() {
		Thread.currentThread().setName("主线程");
		// 调用a对象的foo方法
		a.foo(b);
		System.out.println("进入了主线程之后");
	}

	public void run() {
		Thread.currentThread().setName("副线程");
		// 调用b对象的bar方法
		b.bar(a);
		System.out.println("进入了副线程之后");
	}

	public static void main(String[] args) {
		DeadLock dl = new DeadLock();
		new Thread(dl).start();
		dl.init();
	}
}