Question

enum CoffeeSize{               
      BIG(8),   
      HUGE(10),   
      OVERWHELMING(16) {   

       public String getLidCode(){   
            return "A";   
       }   
      };   

    private int ounces;   

    public int getOunces(){   
         return ounces;   
    }    

    CoffeeSize(int ounces){   
        this.ounces = ounces;   
    }   

    public String getLidCode(){   
            return "B";   
    }   
}

这是K＆amp; B 6书中的SCJP 1.6问题。这是常量特定类主体的一个示例，作为SCJP 6的一个特性。如何执行此操作并查看结果输出？

我有两个问题：

我的Java主要方法是什么样的？请帮我执行这部分代码。我无法理解输出的行为。
{1}}方法在Java 1.6中如何在此类主体中工作？

Answer 1

你称之为常量特定类主体的是JLS所指的枚举常量的可选类主体。它被实现为一个匿名的内部类，扩展外部的封闭枚举。因此，在您的情况下，枚举常量OVERWHELMING将是一个扩展CoffeeSize的匿名内部类型，并覆盖方法getLidCode()。在伪代码中，内部类看起来像这样：

class CoffeeSize$1 extends CoffeeSize {
    @Override
    public String getLidCode() {
        return "A";
    }
}

在常量getLidCode()或BIG上调用HUGE将调用基本枚举实现，而在OVERWHELMING上调用相同的方法将调用方法的覆盖版本，因为OVERWHELMING实际上是另一种类型。要进行测试，只需运行代码即可调用不同枚举常量的getLidCode()。

System.out.println(CoffeeSize.BIG.getLidCode());
System.out.println(CoffeeSize.HUGE.getLidCode());
System.out.println(CoffeeSize.OVERWHELMING.getLidCode());

Answer 2

I have executed my answer,as below.Please correct me if im wrong.output is given.

干杯： - ））

public class EnumOverriddenExample {
enum CoffeeSize{               
      BIG(8),   
      HUGE(10),   
      OVERWHELMING(16){   

           public String getLidCode(){   
                return "A";   
           }   
      };

    CoffeeSize(int ounces){   
            this.ounces = ounces;   
    }

    private int ounces;   

    public int getOunces(){   
         return ounces;   
    }   

    public void setOunces(int ounces){   
         this.ounces=ounces;   
    }

    public String getLidCode(){   
            return "B";   
    }   
}  
public static void main(String[] args) {
    // TODO Auto-generated method stub
    System.out.println("CoffeeSize for BIG is "+EnumOverriddenExample.CoffeeSize.BIG.getLidCode());
    System.out.println("CoffeeSize for HUGE is "+EnumOverriddenExample.CoffeeSize.HUGE.getLidCode());
    System.out.println("CoffeeSize for OVERWHELMING is "+EnumOverriddenExample.CoffeeSize.OVERWHELMING.getLidCode());

    System.out.println("CoffeeSize for BIG is "+EnumOverriddenExample.CoffeeSize.BIG.getOunces());
    System.out.println("CoffeeSize for HUGE is "+EnumOverriddenExample.CoffeeSize.HUGE.getOunces());
    System.out.println("CoffeeSize for OVERWHELMING is "+EnumOverriddenExample.CoffeeSize.OVERWHELMING.getOunces());

}

}

Output is below
-----------------------------------
CoffeeSize for BIG is B --> returns "B"
CoffeeSize for HUGE is B -->returns "B"
CoffeeSize for OVERWHELMING is A--constant specific class body returns "A"
CoffeeSize for BIG is 8
CoffeeSize for HUGE is 10
CoffeeSize for OVERWHELMING is 16
------------------------------------

Java 1.6中的枚举类主体功能

2 个答案: