Java中终止正在运行线程

问题：java 中如何让一个正在运行的线程终止掉？

Demo_1:

class TT implements Runnable {
private boolean flag = true;
@Override
public void run() {
int i = 0;
while(flag) {
System.out.println("child thread: "+i++);
}
}
public void shutDowm() {
flag = false;
}
}
class TestThread {
public static void main(String[] args) {
TT tt = new TT();
Thread t = new Thread(tt);
t.start();
for(int i = 0; i < 4; i++) {
System.out.println("the main Thread is running : "+i);
}
System.out.println("Thread main is void");
tt.shutDowm();
}
}

Demo_2:

class TT implements Runnable {
@Override
public void run() {
for(int i = 1; i <= 589; i++){
System.out.println("subThread: "+ i);
}
}
}
class TestThread {
public static void main(String[] args) {
TT tt = new TT();
Thread t = new Thread(tt);
t.start();
try {
t.join();
} catch (InterruptedException e) {
}
for(int i = 0; i < 8; i++) {
System.out.println("main Thread is running : "+i);
}
}
}

Demo_3:

class TT extends Thread {
@Override
public void run() {
for(int i = 1; i <= 5; i++){
System.out.println("subThread: "+ i);
}
}
}
class TestThread {
public static void main(String[] args) {
TT tt = new TT();
tt.start();

Thread dd = new TT();
dd.start();
for(int i = 0; i < 8; i++) {
System.out.println("main Thread is running : "+i);
}
}
}

 运行结果：

main Thread is running : 0
main Thread is running : 1
main Thread is running : 2
subThread: 1
subThread: 1
subThread: 2
subThread: 2
main Thread is running : 3
main Thread is running : 4
main Thread is running : 5
main Thread is running : 6
main Thread is running : 7
subThread: 3
subThread: 4
subThread: 5
subThread: 3
subThread: 4
subThread: 5