(1) 互斥条件:一个资源每次只能被一个进程使用。
(2) 请求与保持条件:一个进程因请求资源而阻塞时,对已获得的资源保持不放。
(3) 不剥夺条件: 进程已获得的资源,在末使用完之前,不能强行剥夺。
(4) 循环等待条件: 若干进程之间形成一种头尾相接的循环等待资源关系。
这四个条件是死锁的必要条件,只要系统发生死锁,这些条件必然成立,而只要上述条件之
一不满足,就不会发生死锁。
- public class test {
- public static void main(String[] args) throws InterruptedException {
- Object obj1 = new Object();
- Object obj2 = new Object();
- Object obj3 = new Object();
- Thread t1 = new Thread(new SyncThread(obj1, obj2), "t1");
- Thread t2 = new Thread(new SyncThread(obj2, obj3), "t2");
- Thread t3 = new Thread(new SyncThread(obj3, obj1), "t3");
- t1.start();
- Thread.sleep(5000);
- t2.start();
- Thread.sleep(5000);
- t3.start();
- }
- }
- class SyncThread implements Runnable{
- private Object obj1;
- private Object obj2;
- public SyncThread(Object o1, Object o2){
- this.obj1=o1;
- this.obj2=o2;
- }
- @Override
- public void run() {
- System.out.printf("我被调用了,怎么办\n");
- String name = Thread.currentThread().getName();
- //System.out.println(name + " acquiring lock on "+obj1);
- synchronized (obj1) {
- System.out.println(name + " acquired lock on "+obj1);
- work();
- System.out.println(name + " acquiring lock on "+obj2);
- synchronized (obj2) {
- System.out.println(name + " acquired lock on "+obj2);
- work();
- }
- System.out.println(name + " released lock on "+obj2);
- }
- System.out.println(name + " released lock on "+obj1);
- System.out.println(name + " finished execution.");
- }
- private void work() {
- try {
- Thread.sleep(10000);
- } catch (InterruptedException e) {
- e.printStackTrace();
- }
- }
- }
- 结果:
我被调用了,怎么办
t1 acquired lock on java.lang.Object@6a780939
我被调用了,怎么办
t2 acquired lock on java.lang.Object@a3d4d85
我被调用了,怎么办
t3 acquired lock on java.lang.Object@2bbc9dfe
t1 acquiring lock on java.lang.Object@a3d4d85
t2 acquiring lock on java.lang.Object@2bbc9dfe
t3 acquiring lock on java.lang.Object@6a780939
来源: http://www.bubuko.com/infodetail-1963282.html