为什么下面代码的输出是Thread [main，5，main]

Question

public class test1 {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Thread t = Thread.currentThread();
        System.out.println(t);
    }
}

为什么上面代码的输出是 - Thread [main，5，main]？ 请解释

Answer 1

  

返回此线程的字符串表示形式，包括线程   名称，优先级和线程组。

来源：https://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html#toString()

Answer 2

因为thread.toString()返回此线程的字符串表示形式，包括线程的名称，优先级和线程组。

Answer 3

因为：

/**
 * Returns a string representation of this thread, including the
 * thread's name, priority, and thread group.
 *
 * @return  a string representation of this thread.
 */
public String toString() {
    ThreadGroup group = getThreadGroup();
    if (group != null) {
        return "Thread[" + getName() + "," + getPriority() + "," +
                       group.getName() + "]";
    } else {
        return "Thread[" + getName() + "," + getPriority() + "," +
                        "" + "]";
    }
}