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