关于线程thread和runnable

Runnable的意思是，你要用代码——也就是run( )方法——来描述一个处理过程，而不是创建一个表示这个处理过程的对象。在如何理解线程方面，一直存在着争议。这取决于，你是将线程看作是对象还是处理过程[68]。如果你认为它是一个处理过程，那么你就摆脱了"万物皆对象"的OO教条。但与此同时，如果你只想让这个处理过程掌管程序的某一部分，那你就没理由让整个类都成为Runnable的。有鉴于此，用内部类的形式将线程代码隐藏起来，通常是个更明智的选择。就像下面这段代码：

//: c13:ThreadVariations.java
// Creating threads with inner classes.
import com.bruceeckel.simpletest.*;
// Using a named inner class:
class InnerThread1 {
  private int countDown = 5;
  private Inner inner;
  private class Inner extends Thread {
    Inner(String name) {
      super(name);
      start();
    }
    public void run() {
      while(true) {
        System.out.println(this);
        if(--countDown == 0) return;
        try {
          sleep(10);
        } catch (InterruptedException e) {
          throw new RuntimeException(e);
        }
      }
    }
    public String toString() {
      return getName() + ": " + countDown;
    }
  }
  public InnerThread1(String name) {
    inner = new Inner(name);
  }
}
// Using an anonymous inner class:
class InnerThread2 {
  private int countDown = 5;
  private Thread t;
  public InnerThread2(String name) {
    t = new Thread(name) {
      public void run() {
        while(true) {
          System.out.println(this);
          if(--countDown == 0) return;
          try {
            sleep(10);
          } catch (InterruptedException e) {
            throw new RuntimeException(e);
          }
        }
      }
      public String toString() {
        return getName() + ": " + countDown;
      }
    };
    t.start();
  }
}
// Using a named Runnable implementation:
class InnerRunnable1 {
  private int countDown = 5;
  private Inner inner;
  private class Inner implements Runnable {
    Thread t;
    Inner(String name) {
      t = new Thread(this, name);
      t.start();
    }
    public void run() {
      while(true) {
        System.out.println(this);
        if(--countDown == 0) return;
        try {
          Thread.sleep(10);
        } catch (InterruptedException e) {
          throw new RuntimeException(e);
        }
      }
    }
    public String toString() {
      return t.getName() + ": " + countDown;
    }
  }
  public InnerRunnable1(String name) {
    inner = new Inner(name);
  }
}
// Using an anonymous Runnable implementation:
class InnerRunnable2 {
  private int countDown = 5;
  private Thread t;
  public InnerRunnable2(String name) {
    t = new Thread(new Runnable() {
      public void run() {
        while(true) {
          System.out.println(this);
          if(--countDown == 0) return;
          try {
            Thread.sleep(10);
          } catch (InterruptedException e) {
            throw new RuntimeException(e);
          }
        }
      }
      public String toString() {
        return Thread.currentThread().getName() +
          ": " + countDown;
      }
    }, name);
    t.start();
  }
}
// A separate method to run some code as a thread:
class ThreadMethod {
  private int countDown = 5;
  private Thread t;
  private String name;
  public ThreadMethod(String name) { this.name = name; }
  public void runThread() {
    if(t == null) {
      t = new Thread(name) {
        public void run() {
          while(true) {
            System.out.println(this);
            if(--countDown == 0) return;
            try {
              sleep(10);
            } catch (InterruptedException e) {
              throw new RuntimeException(e);
            }
          }
        }
        public String toString() {
          return getName() + ": " + countDown;
        }
      };
      t.start();
    }
  }
}
public class ThreadVariations {
  private static Test monitor = new Test();
  public static void main(String[] args) {
    new InnerThread1("InnerThread1");
    new InnerThread2("InnerThread2");
    new InnerRunnable1("InnerRunnable1");
    new InnerRunnable2("InnerRunnable2");
    new ThreadMethod("ThreadMethod").runThread();
    monitor.expect(new String[] {
      "InnerThread1: 5",
      "InnerThread2: 5",
      "InnerThread2: 4",
      "InnerRunnable1: 5",
      "InnerThread1: 4",
      "InnerRunnable2: 5",
      "ThreadMethod: 5",
      "InnerRunnable1: 4",
      "InnerThread2: 3",
      "InnerRunnable2: 4",
      "ThreadMethod: 4",
      "InnerThread1: 3",
      "InnerRunnable1: 3",
      "ThreadMethod: 3",
      "InnerThread1: 2",
      "InnerThread2: 2",
      "InnerRunnable2: 3",
      "InnerThread2: 1",
      "InnerRunnable2: 2",
      "InnerRunnable1: 2",
      "ThreadMethod: 2",
      "InnerThread1: 1",
      "InnerRunnable1: 1",
      "InnerRunnable2: 1",
      "ThreadMethod: 1"
    }, Test.IGNORE_ORDER + Test.WAIT);
  }
} ///:~
InnerThread1创建了一个继承Thread的非匿名内部类，然后在构造函数里创建了一个这个内部类的实例。如果你要用宿主类的方法访问内部类的特殊功能(新方法)的话，这种做法会比较好。但是绝大多数情况下，创建线程的目的，只是要用它的Thread功能，所以不必创建非匿名的内部类。InnerThread2就演示了这个方案:在构造函数里面创建一个继承Thread的匿名内部类，然后把它上传给Thread的reference t。宿主类的其它方法可以通过t访问Thread的接口，它们无需知道这个对象的确切类型。

第三和第四个类重复了前两个类，不过它们都不是Thread，而是Runnable。这么做是想告诉你，用Runnable什么便宜也没占到，相反代码还稍微复杂了一些(也更难读了一些)。所以结论是，除非迫不得已只能用Runnable，否则我会选Thread。

ThreadMethod演示了怎样在方法的内部创建线程。要运行线程的时候就调用方法，线程启动之后方法就返回。如果这个线程不那么重要，只是做一些辅助操作的话，那么相比在构造函数里启动线程，这个方法或许会更好一些