//沒有互斥鎖的情況（可以自己跑跑看運行結果）：
public class LockDemo {
 
// private static Object lock = new Object();
// static確保只有一把鎖
  private int i = 0;
  public void increaseI() {
//   synchronized (lock) {
      for(int k=0;k<10;k++) { // 對i執(zhí)行10次增1操作
        i++;
      }
      System.out.println(Thread.currentThread().getName() + "線程，i現(xiàn)在的值：" + i);
//   }
  }
  public static void main(String[] args) {
    LockDemo ld = new LockDemo();
    int threadNum = 1000;
    // 選擇1000個線程讓結果更加容易觀測到
    MyThread[] threads = new MyThread[threadNum];
    for(int i=0;i<threads.length;i++) {
      threads[i] = new MyThread(ld);
      // 所有線程共用一個LockDemo對象
      threads[i].start();
    }
  }
}
class MyThread extends Thread {
  LockDemo ld;
   
  public MyThread(LockDemo ld) {
    this.ld = ld;
  }
  public void run() {
    ld.increaseI();
  }
}
//加上互斥鎖以后：
public class LockDemo {
  private static Object lock = new Object();
  // static確保只有一把鎖
  private int i = 0;
  public void increaseI() {
    synchronized (lock) {
      for(int k=0;k<10;k++) {
      // 對i執(zhí)行10次增1操作
        i++;
      }
      System.out.println(Thread.currentThread().getName() + "線程，i現(xiàn)在的值：" + i);
    }
  }
  public static void main(String[] args) {
    LockDemo ld = new LockDemo();
    int threadNum = 1000;
    // 選擇1000個線程讓結果更加容易觀測到
    MyThread[] threads = new MyThread[threadNum];
    for(int i=0;i<threads.length;i++) {
      threads[i] = new MyThread(ld);
      // 所有線程共用一個LockDemo對象
      threads[i].start();
    }
  }
}
class MyThread extends Thread {
  LockDemo ld;
  public MyThread(LockDemo ld) {
    this.ld = ld;
  }
  public void run() {
    ld.increaseI();
  }
}