在Java线程代码中“忽略了新实例”警告

Question

因此，我尝试在NetBeans IDE 11.1中运行此代码，它显示“忽略新实例”错误。我的标准教科书在以下代码中没有提及警告。为什么会显示此错误，我该怎么解决？并在构造函数中启动新线程？也有问题吗？

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class NewThread1 implements Runnable {
    Thread t1;
    NewThread1() {
        t1 = new Thread();
        System.out.println("Thread : " + t1.getName());
        t1.start();  //Starting new thread in a constructor
    }

    public void run() {
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("When NewThread.i = " + i);
                t1.sleep(500);
            }
        } catch (Exception e) {
            System.out.println("t1 interrupted.");
        }
        System.out.println("t1 ends.");
    }
}

public class NewClass1 {
    public static void main(String[] args) {
        new NewThread1();  //New Instance Being Ignored 
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("When main.i = " + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            System.out.println("main thread interrupted.");
        }
        System.out.println("Main thread end.");
    }
}