1）加锁顺序（线程按照一定的顺序加锁）
package itheima.com;
public class DeadLock {
public int flag = 1;
//静态对象是类的所有对象共享的
private static Object o1 = new Object(), o2 = new Object();
public void money(int flag) {
this.flag=flag;
if( flag ==1){
synchronized (o1) {
try {
Thread.sleep(500);
} catch (Exception e) {
e.printStackTrace();
}
synchronized (o2) {
System.out.println("当前的线程是"+
Thread.currentThread().getName()+" "+"flag的值"+"1");
}
}
}
if(flag ==0){
synchronized (o2) {
try {
Thread.sleep(500);
} catch (Exception e) {
e.printStackTrace();
}
synchronized (o1) {
System.out.println("当前的线程是"+
Thread.currentThread().getName()+" "+"flag的值"+"0");
}
}
}
}
public static void main(String[] args) {
final DeadLock td1 = new DeadLock();
final DeadLock td2 = new DeadLock();
td1.flag = 1;
td2.flag = 0;
//td1,td2都处于可执行状态，但JVM线程调度先执行哪个线程是不确定的。
//td2的run()可能在td1的run()之前运行
final Thread t1=new Thread(new Runnable(){
public void run() {
td1.flag = 1;
td1.money(1);
}
});
t1.start();
Thread t2= new Thread(new Runnable(){
public void run() {
// TODO Auto-generated method stub
try {
//让t2等待t1执行完
t1.join();//核心代码，让t1执行完后t2才会执行
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
td2.flag = 0;
td1.money(0);
}
});
t2.start();
}
}
结果：
当前的线程是Thread-0 flag的值1
当前的线程是Thread-1 flag的值0
2. 获取锁时加超时时间.
线程尝试获取锁的时候加上一定的时限，超过时限则放弃对该锁的请求，并释放自己占有的锁
if (lock.tryLock(5000, TimeUnit.MILLISECONDS)) {
System.out.println(tName + "获取到锁！");
} else {
System.out.println(tName + "获取不到锁！");
return;
}
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