第五章 线程同步

1. 重入锁

重入锁使用java.util.concurrent.locks.ReentrantLock类来实现。

public class ReenterLock implements Runnable{ // 声明可重入锁，建议声明为static public static ReentrantLock lock = new ReentrantLock(); public static int i = 0; @Override public void run() { for(int j=0; j<10000000; j++) { // 使用可重入锁保护临界资源 lock.lock(); try { i++; } finally { lock.unlock(); } } } public static void main(String[] args) throws InterruptedException { ReenterLock reenterLock = new ReenterLock(); Thread t1 = new Thread(reenterLock); ReenterLock reenterLock2 = new ReenterLock(); Thread t2 = new Thread(reenterLock2); t1.start(); t2.start(); t1.join(); t2.join(); System.out.println(i); } }

重入锁允许多次加锁，但是与之对应的释放锁次数也要一致。