多线程环境中的增量和减量

您的SyncCounter根本不是线程安全的。可变方法的增量和减量应同步。现在，实现此类的正确方法是原子式的。例如：

class SyncCounter {    private final AtomicInteger x;    public SyncCounter() {     this(0);       }    public SyncCounter(int x) {       this.x = new AtomicInteger(x);    }    int getX() {        return x.get();     }    void setX(int x) {        this.x.set(x);    }    int increment() {        return x.incrementAndGet();    }    int decrement() {        return x.decrementAndGet();    }}

和测试代码：

    final Thread incThread = new Thread(() -> {        count.increment();    });    final Thread decThread = new Thread(() -> {        count.decrement();    });    Thread displayThread = new Thread(() -> {        incThread.join();        decThread.join();        System.out.println("Count value : " + count.getX());    });