# 執行緒的順序

在前篇使用了 join() 來控制安排執行緒。那麼執行緒一多，我們可以安排哪些執行緒優先順序是較高的。

> Java 執行緒的優先順序是使用 1\~10來表示，數字大代表優先權較高（意指先執行）。

有兩個函數與優先權相關：

* setPriority() 用來設定優先順序
* getPriority() 用來取得順序之值

而在 setPriority() 的引數可以使用以下三個常用的代碼：

* MAX\_PRIORTY       最大優先權數值
* MIN\_PRIORTY        最小優先權數值
* NORM\_PRIORTY    系統預設

透過範例來了解一下用法吧～

修改[前一篇的範例](/java-15/java-15-join.md#wan-zheng-cheng-shi-ma-zheng-que)：此次建立5個執行緒，並在執行前設定優先權。

首先建立5個執行緒

```
multi_Test apple=new multi_Test("red");
multi_Test banana=new multi_Test("yellow");
multi_Test grape=new multi_Test("purple");
multi_Test cloud =new multi_Test("white");
multi_Test grass=new multi_Test("green");
```

設定優先權（使用常見的代碼）

```
apple.setPriority(Thread.MAX_PRIORITY);
banana.setPriority(Thread.MIN_PRIORITY);
```

除了使用常見代碼之外，也可以直接設定1\~10的引數

```
cloud.setPriority(3);
grass.setPriority(6);
```

## 完整程式碼

```
class multi_Test
{
   private String name;
   public multi_Test(String str)
   {
      name=str;
   }
   public void show()
   {
      for(int i=0;i<3;i++)
      {
         try
         {
            sleep((int)(1000*Math.random()));
         }
         catch(InterruptedException e){}
         System.out.println(name+" 執行中"+this.getPriority());
      }
   }
}

public class multi_thread_3
{
public static void main(String args[])
{
   multi_Test apple=new multi_Test("red");
   multi_Test banana=new multi_Test("yellow");
   multi_Test grape=new multi_Test("purple");
   multi_Test cloud =new multi_Test("white");
   multi_Test grass=new multi_Test("green");

   apple.setPriority(Thread.MAX_PRIORITY);
   banana.setPriority(Thread.MIN_PRIORITY);
   cloud.setPriority(3);
   grass.setPriority(6);

   apple.start();
   banana.start();
   grape.start();
   cloud.start();
   grass.start();
   }
}
```


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