经典的java多线程死锁例子

一、多个锁之间的嵌套产生死锁。

public class DaneLock {
          
   
    public static void main(String[] args) {
        DieLock d1=new DieLock(true);
        DieLock d2=new DieLock(false);
        Thread t1=new Thread(d1);
        Thread t2=new Thread(d2);
        t1.start();
        t2.start();
    }
}
class MyLock{
          
   
    public static Object obj1=new Object();
    public static Object obj2=new Object();
}
class DieLock implements Runnable{
          
   
    private boolean flag;
    DieLock(boolean flag){
        this.flag=flag;
    }
    public void run() {
        if(flag) {
            while(true) {
                synchronized(MyLock.obj1) {
                    System.out.println(Thread.currentThread().getName()+"....if...obj1...");
                    synchronized(MyLock.obj2) {
                        System.out.println(Thread.currentThread().getName()+".....if.....obj2.....");

                    }
                }
            }
        }
        else {
            while(true){
                synchronized(MyLock.obj2) {
                    System.out.println(Thread.currentThread().getName()+"....else...obj2...");
                    synchronized(MyLock.obj1) {
                        System.out.println(Thread.currentThread().getName()+".....else.....obj1.....");

                    }
                }
            }
        }

    }
}

运行结果：

产生死锁原因：线程0 想要得到obj2 锁进行下面的操作，而obj2锁被线程1 所占有。 线程1想得到obj1锁 进行下面的操作，而obj1锁被线程0 所占有。

二、多生产者与多消费者之间的死锁

public class ManyIOput {
          
   

    public static void main(String[] args) {
        Person person=new Person();
        Input in=new Input(person);
        Output out=new Output(person);
        Thread t0=new Thread(in);
        Thread t1=new Thread(in);
        Thread t2=new Thread(out);
        Thread t3=new Thread(out);
        t0.start();
        t1.start();
        t2.start();
        t3.start();
    }
}

class Person{
          
   
    private String name;
    private String age;
    private boolean redux=false;
    private boolean flag=true;
    public synchronized void setPerson() {
        while(redux) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(flag) {
            flag=false;
            this.name="wppppppppppppppppp";
            this.age="18";
        }
        else {
            flag=true;
            this.name="余周周";
            this.age="16";
        }
        redux=true;
        this.notify();

    }

    public synchronized void getPerson(){
        while(!redux) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        System.out.println(name+"--------+-------"+age);
        redux=false;
        this.notify();
    }
}

class Input implements Runnable{
          
   
    private boolean flag=true;
    private Person person;
    Input(Person person){
        this.person=person;
    }
    public void run() {
        while(true){
            person.setPerson();
        }
    }
}

class Output implements Runnable{
          
   
    private Person person;
    Output(Person person){
        this.person=person;
    }
    public void run() {
        while(true) {
            person.getPerson();
        }
    }
}

运行结果为：

产生死锁的原因： 当生产者t0 等待时，notify唤醒了其它三线程中的任意一个，假如唤醒了是生产者t1 那么t1 也进入等待，产生死锁。 解决的办法是，将notify改变成notifyAll 使之将全部线程唤醒，进而避免了死锁。