Java枚举小结

jopen 9年前

  1. 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 }

  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