java lock

多线程访问同一个变量，不进行同步，会造成结果不一致。这里解决方案有很多，使用原子变量。加锁同步，使用synchronized同步。下面是一个lock demo，后面会分析lock实现原理。lock使用的是公平锁还是非公平锁等

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

/**
 * Created by GuanXF on 2017/11/26.
 */
public class TestLock {
    private static Lock lock = new ReentrantLock();
    private static int count = 0 ;
//    private static AtomicInteger count = new AtomicInteger(0);

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(task);
        Thread t2 = new Thread(task1);
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println("count = " + count);
    }

    static Runnable task1 = new Runnable() {
        @Override
        public void run() {
            int index = 10000;
            while(index > 0){
                lock.lock();
                count++;
                lock.unlock();
//                count.incrementAndGet();
                index --;
            }
        }
    };

    static Runnable task = new Runnable() {
        @Override
        public void run() {
            int index = 10000;
            while(index > 0){
                lock.lock();
                count++;
                lock.unlock();
//                count.incrementAndGet();
                index --;
            }
        }
    };
}

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