线程同步synchronized

synchronized只是保证在同一个时刻，其他线程不能访问锁定的资源，但是其他方法或者是变量不能锁定控制的

解决死锁办法之一：
1、将锁的粒度放粗一点（一口气锁住所有资源）

//模拟“锁住”重要资源不能在一段时间类被多个线程使用
public class TestThread implements Runnable{
	TestSync testSync = new TestSync();
	public static void main(String[] args) {
		TestThread thread = new TestThread();
		Thread t1 = new Thread(thread);
		Thread t2 = new Thread(thread);
		Thread t3 = new Thread(thread);
		//设置线程的名字
		t1.setName("t1");
		t2.setName("t2");
		t1.start();
		t2.start();
		t3.start();
	}
	@Override
	public void run() {
		testSync.add(Thread.currentThread().getName());
	}
}

public class TestSync {
	private static int num = 0;
	//下面这个方法不能在同一时间段被多个线程调用
	public synchronized void add(String name){
	//下面是另外一种语法结构
//		synchronized(this){
			num++;
			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			System.out.println("你是第" + num + "个使用");
//		}
	}
}

 

 

可以简单的模拟死锁的情况

public class TestDeadLockMain {
	public static void main(String[]args){
		TestDeadLock t1 = new TestDeadLock();
		TestDeadLock t2 = new TestDeadLock();
		t1.setFlag(0);
		t2.setFlag(1);
		Thread thread1 = new Thread(t1);
		Thread thread2 = new Thread(t2);
		thread1.start();
		thread2.start();
	}
}

package hb.thread;

public class TestDeadLock implements Runnable {

	public int flag = 1;
	public Object obj1 = new Object();
	public Object obj2 = new Object();
	
	public void setFlag(int flag){
		this.flag = flag;
	}
	
	@Override
	public void run() {
		if(0 == flag){
			synchronized(obj1){
				try {
					System.out.println("flag = " + flag);
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				synchronized(obj2){
					System.out.println("second obj2");
				}
			}
		}
		if(1 == flag){
			synchronized(obj2){
				try {
					System.out.println("flag = " + flag);
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				synchronized(obj1){
					System.out.println("second obj1");
				}
			}
		}
	}

}