import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

public class Main {

  public static void main(String[] args) {
    //方法一：繼承Thread
    int i = 0;
//    for(; i < 100; i++){
//      System.out.println(Thread.currentThread().getName() + " " + i);
//      if (i == 5) {
//        ThreadExtendsThread threadExtendsThread = new ThreadExtendsThread();
//        threadExtendsThread.start();
//      }
//    }
    
    //方法二：實現(xiàn)Runnable
//    for(i = 0; i < 100; i++){
//      System.out.println(Thread.currentThread().getName() + " " + i);
//      if (i == 5) {
//        Runnable runnable = new ThreadImplementsRunnable();
//        new Thread(runnable).start();
//        new Thread(runnable).start();
//      }
//    }

    //方法三：實現(xiàn)Callable接口
    Callable<Integer> callable = new ThreadImplementsCallable();
    FutureTask<Integer> futureTask = new FutureTask<>(callable);
    for(i = 0; i < 100; i++){
      System.out.println(Thread.currentThread().getName() + " " + i);
      if (i == 5) {
        new Thread(futureTask).start();
        new Thread(futureTask).start();
      }
    }
    try {
      System.out.println("futureTask ruturn: " + futureTask.get());
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

}

接下來我們來詳細探討下Java 實現(xiàn)多線程的幾種方式

方法一，繼承自Thread

public class ThreadExtendsThread extends Thread {
  private int i;
  @Override
  public void run() {
    for(; i < 100; i++) {
      System.out.println(getName() + " " + i); 
    }
  }
}

run方法為線程執(zhí)行體，ThreadExtendsThread對象即為線程對象。

方法二，實現(xiàn)Runnable接口

public class ThreadImplementsRunnable implements Runnable {
  private int i;
  @Override
  public void run() {
    for(; i < 100; i++){
      System.out.println(Thread.currentThread().getName() + " " + i);
    }
  }
}

run方法為線程執(zhí)行體，使用時New一個Thread對象，Runnable對象作為target傳遞給Thread對象。且同一個Runnable對象可作為多個Thread的target，這些線程均共享Runnable對象的實例變量。

方法三，實現(xiàn)Callable接口

import java.util.concurrent.Callable;

public class ThreadImplementsCallable implements Callable<Integer> {
  private int i;
  
  @Override
  public Integer call() throws Exception {
    for(; i < 100; i++){
      System.out.println(Thread.currentThread().getName() + " " + i);
    }
    return i;
  }
}

Callable接口類似于Runnable接口，但比對方強大，線程執(zhí)行體為call方法，該方法具有返回值和可拋出異常。使用時將Callable對象包裝為FutureTask對象，通過泛型指定返回值類型?？缮院蛘{(diào)用FutureTask的get方法取回執(zhí)行結(jié)果。

您可能感興趣的文章: