Java 创建线程

通过实现 Runnable 接口创建线程

如果您的类打算作为线程执行，那么您可以通过实现 Runnable 接口。您需要遵循以下三个基本步骤 

第 1 步

作为第一步，您需要实现 Runnable 提供的 run() 方法。该方法为线程提供了一个入口点，您将把完整的业务逻辑放入该方法中。以下是 run() 方法的简单语法 

public void run( ) 

第 2 步

作为第二步，您将使用以下代码实例化 Thread 对象构造函数 

Thread(Runnable threadObj, String threadName); 

其中，threadObj 是实现 Runnable 接口的类的实例，threadName 是赋予新线程的名称。

第 3 步

创建 Thread 对象后，您可以通过调用 start() 方法来启动它，该方法执行调用run()方法。以下是 start() 方法的简单语法 -

void start(); 

示例 1

在这个示例中，我们通过实现 Runnable 接口创建一个 RunnableDemo 类。 RunnableDemo 类具有 run() 方法实现。在主类 TestThread 中，我们创建了 RunnableDemo 对象，并使用这些对象创建了两个 Thread 对象。当每个线程对象调用 Thread.start() 方法时，线程开始处理并执行程序。

package com.yxjc123;
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 

通过继承Thread类创建线程

创建线程的第二种方法是使用以下两个简单步骤创建一个继承 Thread 类的新类。这种方法在处理使用 Thread 类中的可用方法创建的多个线程时提供了更大的灵活性。

第 1 步

您将需要重写可用的 run( ) 方法在线程类中。该方法为线程提供了一个入口点，您将把完整的业务逻辑放入该方法中。以下是 run() 方法的简单语法 -

public void run( ) 

第 2 步

创建 Thread 对象后，您可以通过调用 start() 来启动它方法，它执行对 run() 方法的调用。以下是 start() 方法的简单语法 -

void start( ); 

示例 2

这里是重写前面的程序以继承 Thread - 在这个示例中，我们创建了一个 ThreadDemo 类它继承了 Thread 类。我们在 constructor() 方法中调用 super(name) 为线程分配名称，并调用 super.start() 启动线程处理。

package com.yxjc123;
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: main, State: Start
Thread: main, State: Start
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-2, State: Running
Thread: Thread-1, 1
Thread: Thread-1, State: Dead
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-2, State: Dead 

示例 3

在此示例中，我们展示了如何使用 sleep() 方法来延迟处理。它有助于显示输出中的并行处理。我们在 run 方法中添加了 Thread.sleep() 调用。 InterruptedException 被处理为线程在睡眠模式期间可以被中断。

package com.yxjc123;
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) {
			// TODO 自动生成的 catch 块
			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