volatile和synchronized的区别

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volatile与synchronized对数值进行操作时，可以保证数据的正确性，但后者速度更快
代码如下：

public class T7 {

volatile static int num = 0;
static CountDownLatch latch = new CountDownLatch(100);
//volatile线程可见
static volatile AtomicInteger a = new AtomicInteger();

public static void main(String[] args) {
    var s = System.currentTimeMillis();
    for (int i = 0; i < 100; i++) {
        T7 tt = new T7();
        new Thread(T7::ss, "T" + i).start();
    }
    //new Thread(T7::s1).start();
    try {
        latch.await();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    System.out.println(System.currentTimeMillis() - s);
}

static void s1() {
    try {
        latch.await();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    System.out.println(a);
}

synchronized static void ss1() {
    for (int i = 0; i < 1000; i++) {
        num++;
    }
    latch.countDown();
}

static void ss() {
    for (int i = 0; i < 1000; i++) {
        a.incrementAndGet();
    }
    latch.countDown();
}

}

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