Java死锁范例和 对应解决方案

synchronized 没有嵌套 不会死锁

package Java死锁范例;

public class ThreadDeadlock2 {
    //这种  没有嵌套   不会死锁
    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 SyncThread2(obj1, obj2), "t1");
        Thread t2 = new Thread(new SyncThread2(obj2, obj3), "t2");
        Thread t3 = new Thread(new SyncThread2(obj3, obj1), "t3");
 
        t1.start();
        Thread.sleep(5000);
        t2.start();
        Thread.sleep(5000);
        t3.start();
        
        
 
    }
 
}
 
class SyncThread2 implements Runnable{
    private Object obj1;
    private Object obj2;
 
    public SyncThread2(Object o1, Object o2){
        this.obj1=o1;
        this.obj2=o2;
    }
    @Override
    public void run() {
        String name = Thread.currentThread().getName();
        System.out.println(name + " 准备锁"+obj1);
        //这种  没有嵌套   不会死锁
        synchronized (obj1) {
             System.out.println(name + " 锁定 "+obj1);
             work();
             System.out.println("---------------------------------------------------------");
        }
        System.out.println(name + " 释放 锁"+obj1);
        
        System.out.println("---------------------------------------------------------");
        System.out.println(name + "准备锁"+obj2);
        synchronized (obj2) {
            System.out.println(name + " 锁定 "+obj2);
            work();
        }
        System.out.println(name + " 释放锁"+ obj2 );
        
        System.out.println(name + "---------------------> finished execution.");
    }
    
    
    private void work() {
        try {
            Thread.sleep(30000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

结果：

t1 准备锁java.lang.Object@3e9041fa
t1 锁定 java.lang.Object@3e9041fa
t2 准备锁java.lang.Object@a8f72d1
t2 锁定 java.lang.Object@a8f72d1
t3 准备锁java.lang.Object@76f1ebbf
t3 锁定 java.lang.Object@76f1ebbf
---------------------------------------------------------
t1 释放 锁java.lang.Object@3e9041fa
---------------------------------------------------------
t1准备锁java.lang.Object@a8f72d1
---------------------------------------------------------
t1 锁定 java.lang.Object@a8f72d1
t2 释放 锁java.lang.Object@a8f72d1
---------------------------------------------------------
t2准备锁java.lang.Object@76f1ebbf
---------------------------------------------------------
t3 释放 锁java.lang.Object@76f1ebbf
---------------------------------------------------------
t2 锁定 java.lang.Object@76f1ebbf
t3准备锁java.lang.Object@3e9041fa
t3 锁定 java.lang.Object@3e9041fa