一旦创建了一个Thread对象，你可以通过调用start()方法来启动它，这会导致执行run()方法。下面是start()方法的简单语法：
void start();
启动线程的语法
下面是启动线程的语法：
thread_obj.start();
这里，thread_obj是Thread类的对象，start()是Thread类的方法。
通过实现Runnable接口来启动线程
在这个例子中，我们创建了一个名为RunnableDemo的类，该类实现了Runnable接口。RunnableDemo类包含了run()方法的实现。在主类TestThread中，我们创建了RunnableDemo的对象，并使用这些对象创建了两个Thread对象。当在每个线程对象上调用Thread.start()方法时，线程开始处理并且程序被执行。
示例
package com.tutorialspoint;
class RunnableDemo implements Runnable {
private String threadName;
RunnableDemo( String name) {
threadName = name;
System.out.println("Thread: " + threadName + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + threadName + ", " + "State: Running");
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + threadName + ", " + i);
}
System.out.println("Thread: " + threadName + ", " + "State: Dead");
}
}
public class TestThread {
public static void main(String args[]) {
RunnableDemo runnableDemo1 = new RunnableDemo( "Thread-1");
RunnableDemo runnableDemo2 = new RunnableDemo( "Thread-2");
Thread thread1 = new Thread(runnableDemo1);
Thread thread2 = new Thread(runnableDemo2);
thread1.start();
thread2.start();
}
}
输出
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-1, 1
Thread: Thread-1, State: Dead
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-2, State: Dead
通过扩展Thread类来启动线程
下面是前面的程序重写以扩展Thread类。在这个例子中，我们创建了一个名为ThreadDemo的类，该类扩展了Thread类。我们在构造函数中调用super(name)来给线程命名，并且调用super.start()来启动线程处理。
示例
package com.tutorialspoint;
class ThreadDemo extends Thread {
ThreadDemo( String name) {
super(name);
System.out.println("Thread: " + name + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Running");
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + i);
}
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Dead");
}
public void start () {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Start");
super.start();
}
}
public class TestThread {
public static void main(String args[]) {
ThreadDemo thread1 = new ThreadDemo( "Thread-1");
ThreadDemo thread2 = new ThreadDemo( "Thread-2");
thread1.start();
thread2.start();
}
}
输出
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-1, 1
Thread: Thread-1, State: Dead
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-2, State: Dead
使用sleep()方法启动线程
在这个例子中，我们创建了ThreadDemo类的一些Thread对象，该类扩展了Thread类。我们在构造函数中调用super(name)来给线程命名，并且调用super.start()来启动线程处理。使用sleep()方法，我们在处理中引入了延迟。
示例
package com.tutorialspoint;
class ThreadDemo extends Thread {
ThreadDemo( String name) {
super(name);
System.out.println("Thread: " + name + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Running");
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + i);
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Dead");
}
public void start () {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Start");
super.start();
}
}
public class TestThread {
public static void main(String args[]) {
ThreadDemo thread1 = new ThreadDemo( "Thread-1");
ThreadDemo thread2 = new ThreadDemo( "Thread-2");
thread1.start();
thread2.start();
}
}
输出
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: main, State: Start
Thread: main, State: Start
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-1, 1
Thread: Thread-1, State: Dead
Thread: Thread-2, State: Dead