Java垃圾回收无效线程吗？

测试结果表明：线程在无效之后，GC会回收无效线程，参考附图由原先的18个线程编程12个线程

测试代码：

public class ThreadTest {

    public static void main(String[] args) {
        ThreadTest threadTest = new ThreadTest();
        threadTest.test();
        
    }

    public void test() {
        new W().start();
        new W().start();
        new W().start();
        new W().start();
        while (true) {

        }
    }

    public class W extends Thread {
        public void run() {
            try {
                Thread.sleep(90000);
                System.out.println("1");
            } catch (Exception e) {

            }
        }
    }
}