this的用法 - thread(this, ThreadName)对于Java中这个语句，this是什么？还有Thread为什么需要一个this？

Question

就拿这个程序为例。
public class GetCurrentThread implements Runnable {
Thread th;

public GetCurrentThread(String threadName) {
th = new Thread(this,threadName); //<----DOUBT
System.out.println("get threadname "+th.getName());
th.start();
}

public void run() {
System.out.println(th.getName()+" is starting.....");
System.out.println("Current thread name : " + Thread.currentThread().getName());
}

public static void main(String args[]) {
System.out.println("Current thread name : " + Thread.currentThread().getName());
new GetCurrentThread("1st Thread");
//new GetCurrentThread("2nd Thread");
}
}

Answer 1

首先，这是一个构造函数，SDK说明如下

public Thread(Runnable target,
String name)
Allocates a new Thread object. This constructor has the same effect as Thread (null, target, name).
Parameters:
target - the object whose run method is invoked when this thread is started. If null, this thread's run method is invoked.
name - the name of the new thread

两个参数Runnable和String类型，你的GetCurrentThread实现了Runnable接口，这里的this是代表当前对象，恰好这里的当前对象是一个Runnable。

Answer 2

Thread要的不是this，它要一个Runnable，在你的代码里，刚好this是一个Runnable，所以就这么写了。