Java 简明教程

Java - Creating a Thread

在 Java 中有两种创建线程的不同方法。我们已将其列出如下：

通过实现 Runnable 接口
通过扩展 Thread 类

Create a Thread by Implementing a Runnable Interface

如果准备将您的类作为线程执行，那么可以通过实现 Runnable 接口实现此目的。您需要遵循三个基本步骤 −

Step 1

第一步，您需要实现 Runnable 接口提供的 run() 方法。此方法为线程提供了一个入口点，您需要将完整业务逻辑放入此方法内。以下是 run() 方法的一个简单语法：

public void run( )

Step 2

作为第二步，您将使用以下构造函数实例化一个 Thread 对象 −

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。

Step 3

创建 Thread 对象后，可通过调用 start() method 来启动它，它会执行调用 run( ) 方法。以下是 start() 方法的简单语法：

void start();

Example to Create a Thread by Implementing a Runnable Interface

在本示例中，我们通过实现 Runnable 接口来创建一个类 RunnableDemo。RunnableDemo 类具有 run() 方法实现。在 main 类 TestThread 中，我们创建了 RunnableDemo 对象，并且使用这些对象我们创建了两个 Thread 对象。在每个线程对象上调用 Thread.start() 方法时，线程开始处理并且执行程序。

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();
   }
}

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

Create a Thread by Extending a Thread Class

创建线程的第二种方法是，使用以下两个简单步骤，创建一个扩展 Thread 类的类。这种方法提供了更多灵活性，可使用 Thread class 中的可用方法来处理创建的多个线程。

Step 1

您需要覆盖 Thread 类中可用的 run() method 。此方法为线程提供了一个入口点，您需要将您的完整业务逻辑放入此方法中。以下是 run() 方法的简单语法：

public void run( )

Step 2

一旦创建 Thread 对象，便可以通过调用 start() 方法来启动它，该调用会执行一个 run( ) 方法调用。以下是 start() 方法的一个简单语法 −

void start( );

Example to Create a Thread by Extending a Thread Class

下面是对继承 Thread 的程序的重写 - 在本示例中，我们创建了一个扩展 Thread 类的 ThreadDemo 类。我们在 constructor() 方法中调用 super(name) 为线程分配一个名称，并且调用 super.start() 来启动线程处理。

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();
   }
}

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

Example: Demonstrating sleep() Method

在此示例中，我们展示了使用 sleep() method 来延迟处理。它有助于在输出中显示并行处理。我们在 run 方法中添加了 Thread.sleep() 调用。InterruptedException 被处理，因为线程在睡眠模式期间可能被中断。

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) {
			// TODO Auto-generated catch block
			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();
   }
}

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