java枚举小结

1. 如何定义一个枚举类？

   //定义了4个等级
   enum Level{
       A，B，C，D
   }

2.  枚举类的实质：

   class Level{
       public static final Level A = new Level();
       public static final Level B = new Level();
       public static final Level C = new Level();
       public static final Level D = new Level();
   }

3. 枚举类可以定义构造方法，属性，方法

   enum Level{
       A("85~100","优"),
       B("75~84","良"),
       C("60~74","中"),
       D("60以下","差");
       private String score;
       private String ctype;
       private  Level(String score,String ctype){     //构造方法必须是私有的
           this.score = score ;
           this.ctype = ctype;
       }
       public String getscore(){
           return this.score;
       }
       public String getctpye(){
           return this.ctype;
       }
   }
   public class Enumation {
       public static void main(String[] args) {
           System.out.println(Level.A.getscore());
           System.out.println(Level.A.getctpye());
           Level[] ls = Level.values();
       }
   }
   //输出结果
   //85~100
   //优

4. 带抽象方法的枚举类

   enum Level{
       A("85~100"){
           @Override
           public String getctpye() {
               return "优";
           }
       },
       B("75~84") {
           @Override
           public String getctpye() {
               return "良";
           }
       },
       C("60~74") {
           @Override
           public String getctpye() {
               return "中";
           }
       },
       D("60以下") {
           @Override
           public String getctpye() {
               return "差";
           }
       };
       private String score;
       private  Level(String score){
           this.score = score ;
       }
       public String getscore(){
           return this.score;
       }
       public abstract String getctpye();  //每个对象都要重写抽象方法
   
   }

5.  常用方法

   public class Enumation {
       public static void main(String[] args) {
           System.out.println(Level.C.name()); //返回枚举常量的名称
           System.out.println(Level.C.ordinal()); //返回枚举常量的序号（下标从0开始）
           Level[] ls = Level.values();        //遍历枚举类型
           for(Level l :ls){
               System.out.println(l);
           }
           String letter = "B" ;        
           //返回带指定名称的指定枚举类型的枚举常量，若letter为非枚举类型会抛异常java.lang.IllegalArgumentException: No enum constant 
           Level b = Level.valueOf(letter);
           System.out.println(b.B);
       }
   }
   　　

   输出：
   C
   2
   A
   B
   C
   D
   B