创建并启动线程的三种方法

方法一：public class Demo extends Thread {

public void run() {
int i=0 ;
for( ;i<100;i++) {
System.out.println(Thread.currentThread().getName() + " : " + i);
}
}
public static void main(String[] args) {

for(int i=0 ;i<100 ;i++) {
System.out.println(Thread.currentThread().getName() + " : " + i);
if(i==20) {
new Demo().start();
new Demo().start();
}
}
}
}
方法二：public class Demo implements Runnable {

@Override
public void run() {
int i=0 ;
for(;i<100;i++) {
System.out.println(Thread.currentThread().getName() + " : " + i);
}
}
public static void main(String[] args) {
for(int i=0 ;i<100 ;i++) {
System.out.println(Thread.currentThread().getName() + " : " + i);
if(i==20) {
Demo target = new Demo() ;
new Thread(target, "新线程2").start();
new Thread(target, "新线程2").start();
}
}
}
}方法三：import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

public class Demo {

public static void main(String[] args) throws Exception {
FutureTask<Integer> futureTask = new FutureTask<>((Callable<Integer>)() -> {
int i=0 ;
for(;i<100;i++) {
System.out.println(Thread.currentThread().getName() + " : " + i);
}
return i ;
}) ;
for(int i=0 ;i<100 ;i++) {
System.out.println(Thread.currentThread().getName() + " : " + i);
if(i==20) {
new Thread(futureTask, "有返回值线程1").start();
new Thread(futureTask, "有返回值线程2").start();
}

}
System.out.println("返回值为：" + futureTask.get()); ;
}

}