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java枚举小结

如何定义一个枚举类？

1 //定义了4个等级 2 enum Level{ 3     A，B，C，D 4 }

枚举类的实质：

1 class Level{ 2     public static final Level A = new Level(); 3     public static final Level B = new Level(); 4     public static final Level C = new Level(); 5     public static final Level D = new Level(); 6 }

枚举类可以定义构造方法，属性，方法

 1 enum Level{  2     A("85~100","优"),  3     B("75~84","良"),  4     C("60~74","中"),  5     D("60以下","差");  6     private String score;  7     private String ctype;  8     private  Level(String score,String ctype){     //构造方法必须是私有的  9         this.score = score ; 10         this.ctype = ctype; 11     } 12     public String getscore(){ 13         return this.score; 14     } 15     public String getctpye(){ 16         return this.ctype; 17     } 18 } 19 public class Enumation { 20     public static void main(String[] args) { 21         System.out.println(Level.A.getscore()); 22         System.out.println(Level.A.getctpye()); 23         Level[] ls = Level.values(); 24     } 25 } 26 //输出结果 27 //85~100 28 //优

带抽象方法的枚举类

 1 enum Level{  2     A("85~100"){  3         @Override  4         public String getctpye() {  5             return "优";  6         }  7     },  8     B("75~84") {  9         @Override 10         public String getctpye() { 11             return "良"; 12         } 13     }, 14     C("60~74") { 15         @Override 16         public String getctpye() { 17             return "中"; 18         } 19     }, 20     D("60以下") { 21         @Override 22         public String getctpye() { 23             return "差"; 24         } 25     }; 26     private String score; 27     private  Level(String score){ 28         this.score = score ; 29     } 30     public String getscore(){ 31         return this.score; 32     } 33     public abstract String getctpye();  //每个对象都要重写抽象方法 34  35 }

常用方法

 1 public class Enumation {  2     public static void main(String[] args) {  3         System.out.println(Level.C.name()); //返回枚举常量的名称  4         System.out.println(Level.C.ordinal()); //返回枚举常量的序号（下标从0开始）  5         Level[] ls = Level.values();        //遍历枚举类型  6         for(Level l :ls){  7             System.out.println(l);  8         }  9         String letter = "B" ;         10         //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  11         Level b = Level.valueOf(letter); 12         System.out.println(b.B); 13     } 14 }