java thread lock details and example code

java thread lock

Use the synchronized keyword in the Java thread to achieve synchronization

synchronized can lock methods, lock classes, lock objects, lock code blocks

Methods the lock

//  The synchronization lock is added to the method this
  public synchronized void print() {
    System.out.println(" Synchronized methods ");
    try {
      Thread.sleep(3000);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }

Kind of lock

public synchronized void print(String msg) {
    //  Kind of lock 
    synchronized (MyThread.class) {
      System.out.println(msg);
      try {
        Thread.sleep(3000);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
  }

Object lock

Take selling train tickets

public class Window extends Thread {

  public Window(String name) {
    super(name);
  }

  static int tick = 100;
  static String obj = new String();

  @Override
  public void run() {
    //  Start selling tickets 
    while (tick > 0) {
      //  Synchronized code block 
      // 1 The lock   The key 
      //  All threads   You have to line up here 
      synchronized (obj) {
        if (tick > 0) {
          System.out.println(getName() + " Sold the first one. " + tick + " 】 a ticket ");//  lost cpu resources 
          tick--;
        }
      }
      try {
        Thread.sleep(100);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }

  }
}

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