Java 源码分析-ReentrantLock 类

ReentrantLock 介绍

ReentrantLock 是一个可重入且独占式的锁，它具有与使用 synchronized 监视器锁相同的基本行为和语义，但与 synchronized 关键字相比，它更灵活、更强大。

使用示例

public class Test {
    private Lock lock = new ReentrantLock();
    private Condition condition = lock.newCondition();
    private int count;

    public void add() {
        lock.lock();
        try {
            while (count != 0) {
                condition.await();
            }
            count ++;
            System.out.println("加加");
            condition.signalAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void subtract() {
        lock.lock();
        try {
            while (count == 0) {
                condition.await();
            }
            count --;
            System.out.println("减减");
            condition.signalAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public static void main(String[] args) throws Exception{
        Test t = new Test();
        new Thread(()->{
            for(int i=0; i<100; i++)
                t.add();
        }).start();
        new Thread(()->{
            for(int i=0; i<100; i++)
                t.subtract();
        }).start();
    }
}

结果：
加加
减减
加加
减减
......

构造方法

public ReentrantLock() {
    sync = new NonfairSync();
}

public ReentrantLock(boolean fair) {
    sync = fair ? new FairSync() : new NonfairSync();
}