Java - 建立執行緒

在 Java 中建立執行緒有兩種不同的方法。我們已將它們列出如下：

• 透過實現 Runnable 介面
• 透過擴充套件 Thread 類

透過實現 Runnable 介面建立執行緒

如果您的類旨在作為執行緒執行，那麼您可以透過實現Runnable介面來實現這一點。您需要遵循三個基本步驟：

步驟 1

第一步，您需要實現Runnable介面提供的run()方法。此方法為執行緒提供了一個入口點，您將在此方法中放置完整的業務邏輯。以下是run()方法的簡單語法：

public void run( )

步驟 2

第二步，您將使用以下建構函式例項化一個Thread物件：

Thread(Runnable threadObj, String threadName);

其中，threadObj是實現Runnable介面的類的例項，threadName是賦予新執行緒的名稱。

步驟 3

建立 Thread 物件後，您可以透過呼叫start()方法來啟動它，該方法會執行對run()方法的呼叫。以下是start()方法的簡單語法：

void start();

透過實現 Runnable 介面建立執行緒的示例

在此示例中，我們透過實現 Runnable 介面來建立一個名為 RunnableDemo 的類。RunnableDemo 類具有 run() 方法的實現。在主類 TestThread 中，我們建立了 RunnableDemo 物件，並使用這些物件建立了兩個 Thread 物件。當在每個執行緒物件上呼叫 Thread.start() 方法時，執行緒開始處理，程式執行。

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();
   }
}

輸出

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

透過擴充套件 Thread 類建立執行緒

建立執行緒的第二種方法是建立一個擴充套件Thread類的新類，使用以下兩個簡單的步驟。這種方法在處理使用Thread 類中可用方法建立的多個執行緒時提供了更大的靈活性。

步驟 1

您需要重寫run()方法，該方法在 Thread 類中可用。此方法為執行緒提供了一個入口點，您將在此方法中放置完整的業務邏輯。以下是run()方法的簡單語法：

public void run( )

步驟 2

建立 Thread 物件後，您可以透過呼叫start()方法來啟動它，該方法會執行對run()方法的呼叫。以下是start()方法的簡單語法：

void start( );

透過擴充套件 Thread 類建立執行緒的示例

以下是重寫為擴充套件 Thread 的前一個程式：在此示例中，我們建立了一個 ThreadDemo 類，該類擴充套件了 Thread 類。我們在建構函式()方法中呼叫 super(name) 為執行緒分配名稱，並呼叫 super.start() 啟動執行緒處理。

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();
   }
}

輸出

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，我們展示了sleep()方法的使用來延遲處理。它有助於在輸出中顯示並行處理。我們在 run 方法中添加了 Thread.sleep() 呼叫。InterruptedException 被處理，因為執行緒在休眠模式下可能會被中斷。

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();
   }
}

輸出

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