Java学习-死锁练习

3个同步对象a, b, c
3个线程 t1,t2,t3
故意设计场景，使这3个线程彼此死锁

package multiplethread;

import charactor.Hero;

public class Test5 {
    public static void main(String[] args) {
          Hero a=new Hero("a");
          Hero b=new Hero("b");
          Hero c=new Hero("c");
          Thread t1=new Thread(){
              public void run(){
                  synchronized (a) {
                    System.out.println("t1已经占有a");
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    System.out.println("t1试图占有b");
                    synchronized (b) {
                        System.out.println("占有成功");
                    }
                }
              }
          };
          t1.start();
          Thread t2=new Thread(){
              public void run(){
                  synchronized (b) {
                    System.out.println("t2已经占有b");
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    System.out.println("t2试图占有c");
                    synchronized (c) {
                        System.out.println("占有成功");
                    }
                }
              }
          };
          t2.start();
          Thread t3=new Thread(){
              public void run(){
                  synchronized (c) {
                    System.out.println("t3已经占有c");
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    System.out.println("t3试图占有a");
                    synchronized (a) {
                        System.out.println("占有成功");
                    }
                }
              }
          };
          t3.start();
    }
}

效果图：

使用Lock方式的死锁测试

令线程t1，t2分别占有lock1，lock2对象，二者再试图占有对方的对象

package multiplethread;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Test {

    public static void main(String[] args) {
        Lock lock1 = new ReentrantLock();
        Lock lock2 = new ReentrantLock();
        // lock1 lock2对象互相尝试占有对方
        Thread t1 = new Thread() {
            boolean locked1 = false;// 开始时lock1未被占有
            boolean locked1_2 = false;
            public void run() {
                try {
                    locked1 = lock1.tryLock(1, TimeUnit.SECONDS);
                    if (locked1) {
                        System.out.println(this.getName() + "成功占有lock1");
                        System.out.println("试图再占有lock2");
                        try {
                            locked1_2 = lock2.tryLock();
                            if (locked1_2)
                                System.out.println(this.getName() + "成功占有lock2");
                            else
                                System.out.println(this.getName() + "占有失败");
                        } finally {
                            if (locked1_2) {
                                System.out.println(this.getName() + "释放对象lock2");
                                lock2.unlock();
                            }
                        }
                    } else
                        System.out.println(this.getName() + "放弃了占有lock1");
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } finally {
                    if (locked1) {
                        System.out.println(this.getName() + "释放对象lock1");
                        lock1.unlock();
                    }
                }
            }
        };
        t1.setName("t1");
        t1.start();
        Thread t2 = new Thread() {
            boolean locked2 = false;// 开始时lock2未被占有
            boolean locked2_1 = false;
            public void run() {
                try {
                    locked2 = lock2.tryLock(1, TimeUnit.SECONDS);
                    if (locked2) {
                        System.out.println(this.getName() + "成功占有lock2");
                        System.out.println("试图再占有lock1");
                        try {
                            locked2_1 = lock1.tryLock();
                            if (locked2_1)
                                System.out.println(this.getName() + "成功占有lock1");
                            else
                                System.out.println(this.getName() + "占有失败");
                        } finally {
                            if (locked2_1) {
                                System.out.println(this.getName() + "释放对象lock1");
                                lock1.unlock();
                            }
                        }
                    } else
                        System.out.println(this.getName() + "放弃了占有lock1");
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } finally {
                    if (locked2) {
                        System.out.println(this.getName() + "释放对象lock2");
                        lock2.unlock();
                    }
                }
            }
        };
        t2.setName("t2");
        t2.start();

    }
}

效果图：

 并且运行顺利结束，没有死循环出现，说明Lock的trylock方式成功避免了死锁。