synchronized:线程同步方法使用总结

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synchronized:
1.多线程执行同一对象的synchronized函数，线程同步正确；

实例代码如下：
public class Test1 implements Runnable{

//定义同一对象

static Test2 action;

public static void main(String[] args) {
  // TODO Auto-generated method stub

  Class cls;
  try {
   cls = Class.forName("Test2");
      action = (Test2) cls.newInstance();
   Test1 t1 = new Test1();
   for (int i=0;i<1;i++){
    new Thread(t1).start();
    new Thread(t1).start();
    new Thread(t1).start();
    new Thread(t1).start();
   }
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
}

public void run() {
  // TODO Auto-generated method stub
  try {
                action.getRandomString();
   } catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
}
}

public class Test2 {

public static void main(String[] args) {

}
    //调用同一对象的synchronized 函数，无需加statci修饰
public synchronized void getRandomString() throws InterruptedException {
  System.out.println("$$$$$$$$$$$$$$$$$$");
  Thread.sleep(1000);
  Random random = new Random();
        int aa = random.nextInt(10);
        int bb = random.nextInt(10);
        int cc = random.nextInt(10);
  System.out.println(String.valueOf(aa)+String.valueOf(bb)+String.valueOf(cc));
  System.out.println("############");
}
}
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   2.多线程执行不同对象的synchronized函数，线程同步错误；

实例代码如下：
public class Test1 implements Runnable{

public static void main(String[] args) {
  try {
   Test1 t1 = new Test1();
   for (int i=0;i<100;i++){
    new Thread(t1).start();
    new Thread(t1).start();
    new Thread(t1).start();
    new Thread(t1).start();
   }
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
}

public void run() {
  // TODO Auto-generated method stub
  Class cls;
   try {
    cls = Class.forName("Test2");
    Test2 action = (Test2) cls.newInstance();
                action.getRandomString();
   } catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
}
}

public class Test2 {

public static void main(String[] args) {

}

/**
* @param args
* @throws InterruptedException
*/
//调用不同对象的synchronized 函数，需要加statci修饰，否则线程同步失败
public synchronized void getRandomString() throws InterruptedException {
  System.out.println("$$$$$$$$$$$$$$$$$$");
  Thread.sleep(1000);
  Random random = new Random();
        int aa = random.nextInt(10);
        int bb = random.nextInt(10);
        int cc = random.nextInt(10);
  System.out.println(String.valueOf(aa)+String.valueOf(bb)+String.valueOf(cc));
  System.out.println("############");
}
}
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=====================================================
   3.多线程执行不同对象的synchronized static 函数，线程同步正确；

实例代码如下：
public class Test1 implements Runnable{

public class Test2 {

public static void main(String[] args) {

}

/**
* @param args
* @throws InterruptedException
*/
//调用不同对象的synchronized 函数，需要加statci修饰，否则线程同步失败
public synchronized static void getRandomString() throws InterruptedException {
  System.out.println("$$$$$$$$$$$$$$$$$$");
  Thread.sleep(1000);
  Random random = new Random();
        int aa = random.nextInt(10);
        int bb = random.nextInt(10);
        int cc = random.nextInt(10);
  System.out.println(String.valueOf(aa)+String.valueOf(bb)+String.valueOf(cc));
  System.out.println("############");
}
}

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