死锁示例
由于两个锁对象lock1,lock2是static只存在一份,导致两个线程执行时会相互等待已经被获得的琐对象,导致死锁产生.
如果将static去掉,2个锁对象就是线程独有的变量,不会被别的线程发现,因此不会产生死锁.
public class DeadLock implements Runnable{
private String tag;
private static Object lock1 = new Object();
private static Object lock2 = new Object();
public void setTag(String tag){
this.tag = tag;
}
@Override
public void run() {
if(tag.equals("a")){
synchronized (lock1) {
try {
System.out.println("当前线程 : " + Thread.currentThread().getName() + " 进入lock1执行");
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (lock2) {
System.out.println("当前线程 : " + Thread.currentThread().getName() + " 进入lock2执行");
}
}
}
if(tag.equals("b")){
synchronized (lock2) {
try {
System.out.println("当前线程 : " + Thread.currentThread().getName() + " 进入lock2执行");
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (lock1) {
System.out.println("当前线程 : " + Thread.currentThread().getName() + " 进入lock1执行");
}
}
}
}
public static void main(String[] args) {
DeadLock d1 = new DeadLock();
d1.setTag("a");
DeadLock d2 = new DeadLock();
d2.setTag("b");
Thread t1 = new Thread(d1, "t1");
Thread t2 = new Thread(d2, "t2");
t1.start();
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
t2.start();
}
}
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