Lock的tryLock()方法

概述

tryLock 是防止自锁的一个重要方式。

tryLock()方法是有返回值的，它表示用来尝试获取锁，如果获取成功，则返回true，如果获取失败（即锁已被其他线程获取），则返回false，这个方法无论如何都会立即返回。在拿不到锁时不会一直在那等待。

package test;
 
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
//学习 tryLock
//tryLock()方法是有返回值的，它表示用来尝试获取锁，如果获取成功，则返回true，如果获取失败（即锁已被其他线程获取），则返回false，这个方法无论如何都会立即返回。在拿不到锁时不会一直在那等待。
public class tryLock {
 
    public static void main(String[] args) {
         
        System.out.println("开始");
        final Lock lock = new ReentrantLock();
        new Thread() {
            @Override
            public void run() {
                String tName = Thread.currentThread().getName();
                if (lock.tryLock()) {
                    System.out.println(tName + "获取到锁！");
                } else {
                    System.out.println(tName + "获取不到锁！");
                    return;
                }
                try {
                    for (int i = 0; i < 5; i++) {
                        System.out.println(tName + ":" + i);
                    }
                    Thread.sleep(5000);
                } catch (Exception e) {
                    System.out.println(tName + "出错了！！！");
                } finally {
                    System.out.println(tName + "释放锁！！");
                    lock.unlock();
                }
 
            }
        }.start();
 
        new Thread() {
            @Override
            public void run() {
                String tName = Thread.currentThread().getName();
 
                if (lock.tryLock()) {
                    System.out.println(tName + "获取到锁！");
                } else {
                    System.out.println(tName + "获取不到锁！");
                    return;
                }
 
                try {
                    for (int i = 0; i < 5; i++) {
                        System.out.println(tName + ":" + i);
                    }
 
                } catch (Exception e) {
                    System.out.println(tName + "出错了！！！");
                } finally {
                    System.out.println(tName + "释放锁！！");
                    lock.unlock();
                }
            }
        }.start();
         
        System.out.println("结束");
    }
}