JAVA多线程 访问多个对象并发问题

我们知道当两个并发线程(thread1和thread2)访问同一个对象(syncThread)时,可以用synchronized加锁,代码如下:

public static void main(String[] args) {
         SyncThread syncThread = new SyncThread();
        Thread thread1 = new Thread( syncThread , "SyncThread1");
        Thread thread2 = new Thread( syncThread , "SyncThread2");
        thread1.start();
        thread2.start();
    }

public  void run() {
       {
            for (int i = 0; i < 5; i++) {
                try {
                    System.out.println("线程名:"+Thread.currentThread().getName() + ":" + (count++));
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

但是如果访问的是不同对象,那么应该怎么去处理并发的情况,因为在实际应用中遇到了这种情况

public static void main(String[] args) {
        System.out.println("使用关键字synchronized每次调用进行new SyncThread()");
        SyncThread syncThread1 = new SyncThread();
        SyncThread syncThread2 = new SyncThread();
        Thread thread1 = new Thread(syncThread1, "SyncThread1");
        Thread thread2 = new Thread(syncThread2, "SyncThread2");
        thread1.start();
        thread2.start();
    }

```

方法很多

可以在 SyncThread 加静态变量方法，如：

class SyncThread {
  private final static Object mLock = new Object();

  void run() {
    synchronized(mLock) {
      ...
    }
  }
}

public class SyncThread implements Runnable {
    private static int count = 0;
    public static int increase(){
        synchronized (SyncThread.class) {
            return count++;
        }
    }

    @Override
    public void run() {
        for (int i = 0; i < 5; i++) {
            try {
                System.out.println("线程名:"+Thread.currentThread().getName() + ":" + increase());
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}