[Java知识库]AvoidDeadLock-TryLockMethod

避免死锁方法--使用tryLock方法

package com.chen.test.Thread.AvoidDeadLock;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

/**
 * 避免线程死锁方式：
 * 1、资源分配顺序是有序的
 * 2、破坏死锁必要条件
 * 3、使用tryLock()方法，tryLock()带返回值的，返回是boolean类型，如果是true说明是获得锁，否则获得锁失败，
 *    与此同时，也可以使用tryLock（long time,TimeUtil.time util）有参方法，设置规定时间，如果在指定时间范围内没有获得锁或者是遇到阻塞
 */
public class TryLockDemo3 {
    private static final Logger log = LoggerFactory.getLogger(TryLockDemo3.class);
    private final ReentrantLock lock1 = new ReentrantLock();
    private final ReentrantLock lock2 = new ReentrantLock();


    public void service(){

        long id = Thread.currentThread().getId();
        String name = Thread.currentThread().getName();
        while (true){
            if(id % 2 ==0){
                try {
                    if (lock1.tryLock()){
                        log.info(name + " get lock1 lock success ! ");
                        Thread.sleep(10);
                        try {
                            if(lock2.tryLock()){
                                log.info(name + " start works !");
                                for (int i = 0; i < 3; i++) {
                                    log.info(name + " i = " + i);
                                }
                                return;
                            }
                        }finally {
                            if(lock2.isHeldByCurrentThread()){
                                log.info(name + " release lock2 lock !");
                                lock2.unlock();
                            }
                        }
                    }
                }catch (InterruptedException ver1){
                    log.error(name + "Throws exception and print exceptions !");
                    ver1.printStackTrace();
                }finally {
                    if (lock1.isHeldByCurrentThread()){
                        log.info(name + " release lock1 lock !");
                        lock1.unlock();
                    }
                }
            }else {
                try {
                    if (lock1.tryLock()){
                        log.info(name + " get lock1 lock success ! ");
                        Thread.sleep(500);
                        try {
                            if(lock2.tryLock()){
                                log.info(name + " start works !");
                                for (int i = 0; i < 3; i++) {
                                    log.info(name + " i = " + i);
                                }
                                return;
                            }
                        }finally {
                            if(lock2.isHeldByCurrentThread()){
                                log.info(name + " release lock2 lock !");
                                lock2.unlock();
                            }
                        }
                    }
                }catch (InterruptedException ver1){
                    log.error(name + "Throws exception and print exceptions !");
                    ver1.printStackTrace();
                }finally {
                    if (lock1.isHeldByCurrentThread()){
                        log.info(name + " release lock1 lock !");
                        lock1.unlock();
                    }
                }
            }
        }
    }

    //main method
    public static void main(String[] args) {
        TryLockDemo3 demo3 = new TryLockDemo3();

        try {
            for (int i = 0; i < 10; i++) {
                new Thread(demo3::service,"Thread-" +i).start();
            }
            Thread.sleep(1000);
        }catch (InterruptedException ver1){
            ver1.printStackTrace();
        }

    }
}

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