Java - 创建线程

在 Java 中创建线程有两种不同的方法。我们已将它们列出如下：

• 通过实现 Runnable 接口
• 通过扩展 Thread 类

通过实现 Runnable 接口创建线程

如果您的类旨在作为线程执行，那么您可以通过实现Runnable接口来实现这一点。您需要遵循三个基本步骤：

步骤 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，您将在此方法中放置完整的业务逻辑。以下是run()方法的简单语法：

public void run( )

步骤 2

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。

步骤 3

创建 Thread 对象后，您可以通过调用start()方法来启动它，该方法会执行对run()方法的调用。以下是start()方法的简单语法：

void start();

通过实现 Runnable 接口创建线程的示例

在此示例中，我们通过实现 Runnable 接口来创建一个名为 RunnableDemo 的类。RunnableDemo 类具有 run() 方法的实现。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。当在每个线程对象上调用 Thread.start() 方法时，线程开始处理，程序执行。

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 类创建线程

创建线程的第二种方法是创建一个扩展Thread类的新类，使用以下两个简单的步骤。这种方法在处理使用Thread 类中可用方法创建的多个线程时提供了更大的灵活性。

步骤 1

您需要重写run()方法，该方法在 Thread 类中可用。此方法为线程提供了一个入口点，您将在此方法中放置完整的业务逻辑。以下是run()方法的简单语法：

public void run( )

步骤 2

创建 Thread 对象后，您可以通过调用start()方法来启动它，该方法会执行对run()方法的调用。以下是start()方法的简单语法：

void start( );

通过扩展 Thread 类创建线程的示例

以下是重写为扩展 Thread 的前一个程序：在此示例中，我们创建了一个 ThreadDemo 类，该类扩展了 Thread 类。我们在构造函数()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.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: 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：演示 sleep() 方法

在此示例中，我们展示了sleep()方法的使用来延迟处理。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，因为线程在休眠模式下可能会被中断。

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();
   }
}

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