Java 多线程 ---- 线程中this与 Thread.currentThread()线程的区别

总结起来一句话：在Thread中调用this其实就是调用Thread私有Runnable类型的target，target是Thread类的一个属性，而Thread.currentThread()是指新New出来的实例Thread类。两个是不同的对象。实例化一个Thread的对象，都会将其赋值给Thread的私有target属性。

直接上代码：

注意代码中红色部分，就可以解释this和Thread.currentThread()的区别。实际上new Thread(Runnable)，new Thread(Runnable,String) 会将一个thread( Thread 是Runnable接口的实现类) 应用的对象绑定到一个pravite变量target上，在t1被执行的时候即t1.run()被调用的时候，它会调用target.run()方法，也就是说它是直接调用thread对象的run方法，再确切的说，在run方法被执行的时候，this.getName()实际上返回的target.getName()，而Thread.currentThread().getName()实际上是t1.getName()。

new Thread(Runnable）的源码

  public Thread(Runnable target) {
         init(null, target, "Thread-" + nextThreadNum(), 0);
     }

 public class TestThread {

     public static void main(String[] args) {
         Bed b = new Bed();
 5         b.start();
 6         Thread t1 = new Thread(b,"B");
         System.out.println("main begin t1 isAlive=" + t1.isAlive());
 //        t1.setName("B");
         t1.start();
         System.out.println("main end t1 isAlive=" + t1.isAlive());

     }
 }

 class Bed extends Thread {

     public Bed() {
         System.out.println("Bed Constructor---begin");
         System.out.println("Thread.currentThread().getName()=" + Thread.currentThread().getName());// 获取线程名
         System.out.println("Thread.currentThread().isAlive()=" + Thread.currentThread().isAlive()); // 查看线程是否存活
         System.out.println("this.getName=" + this.getName());
         System.out.println("this.isAlive()=" + this.isAlive());
         System.out.println("Thread.currentThread()==this :" + (Thread.currentThread() == this));
         System.out.println("Bed Constructor---end ");
     }

     @Override
     public void run() {
         System.out.println("run---begin");
         System.out.println("Thread.currentThread().getName=" + Thread.currentThread().getName());
         System.out.println("Thread.currentThread().isAlive()" + Thread.currentThread().isAlive());
         System.out.println("Thread.currentThread()==this :" + (Thread.currentThread() == this));
         System.out.println("this.getName()=" + this.getName());
         System.out.println("this.isAlive()=" + this.isAlive());
         System.out.println("run --- end");
     }
 }

结果：

 Bed Constructor---begin
 Thread.currentThread().getName()=main
 Thread.currentThread().isAlive()=true
 this.getName=Thread-0
 this.isAlive()=false
 Thread.currentThread()==this :false
 Bed Constructor---end
 main begin t1 isAlive=false
 run---begin
 Thread.currentThread().getName=Thread-0
 Thread.currentThread().isAlive()true
 Thread.currentThread()==this :true
 this.getName()=Thread-0
 this.isAlive()=true
 run --- end
 main end t1 isAlive=true
 run---begin
 Thread.currentThread().getName=B
 Thread.currentThread().isAlive()true
 Thread.currentThread()==this :false
 this.getName()=Thread-0
 this.isAlive()=false
 run --- end

b.start()的时候，就是调用Thread的run方法，而newThread对象的时候将其赋给target对象，如果未指定名称系统默认给target命名，target是线程类Thread的一个私有Runnable类型属性。

     private Runnable target;

即使将target和new Thread的线程赋值一样的名称也不会出现this==Thread.currentThread()，从而说明target和new Thread()是两个不同的对象。

 public class TestThread {

     public static void main(String[] args) {

         Bed b = new Bed("A");
         b.start();
         Thread t1 = new Thread(b,"A");
         System.out.println("main begin t1 isAlive=" + t1.isAlive());
         t1.start();
         System.out.println("main end t1 isAlive=" + t1.isAlive());

     }

 }

结果：

 Bed Constructor---begin
 Thread.currentThread().getName()=main
 Thread.currentThread().isAlive()=true
 this.getName=A
 this.isAlive()=false
 Thread.currentThread()==this :false
 Bed Constructor---end
 run---begin
 Thread.currentThread().getName=A
 Thread.currentThread().isAlive()true
 Thread.currentThread()==this :true
 this.getName()=A
 this.isAlive()=true
 run --- end
 main begin t1 isAlive=false
 main end t1 isAlive=true
 run---begin
 Thread.currentThread().getName=A
 Thread.currentThread().isAlive()true
 Thread.currentThread()==this :false
 this.getName()=A
 this.isAlive()=false
 run --- end

Reference

[1] https://www.cnblogs.com/huangyichun/p/6071625.html