java枚举详解

枚举的本质是类，枚举是用来构建常量数据结构的模板（初学者可以以此方式理解: public static final X=xxx），枚举的使用增强了程序的健壮性，在引用一个不存在的枚举值的时候，编译器会报错。

案例1：　　

public enum Grade {
    A,B,C,D
}

public class Test {
    public static void main(String[] args) {
        System.out.println(Grade.A);
        System.out.println(Grade.B);
        System.out.println(Grade.C);
        System.out.println(Grade.D);
    }
}

结果输出:　

　　A   B  C  D

案例2：

public enum Grade {
    A("81-100"),B("71-80"),C("61-70"),D("0-60");
    private String value;
    private Grade(String value){
        this.value=value;
    }
    public String getValue(){
        return this.value;
    }
}

public class Test {
    public static void main(String[] args) {
        System.out.println(Grade.A);
        System.out.println(Grade.A.getValue());
        System.out.println(Grade.B);
        System.out.println(Grade.B.getValue());
        System.out.println(Grade.C);
        System.out.println(Grade.C.getValue());
        System.out.println(Grade.D);
        System.out.println(Grade.D.getValue());
    }
}

结果：

　　A 81-100 B 71-80 C 61-70 D 0-60

案例3：

public enum Grade {

    A("81-100") {
        @Override
        public String toLocalString() {
            return "优";
        }
    },B("71-80") {
        @Override
        public String toLocalString() {
            return "良";
        }
    },C("61-70") {
        @Override
        public String toLocalString() {
            return "中";
        }
    },D("0-60") {
        @Override
        public String toLocalString() {
            return "差";
        }
    };

    private String value;

    private Grade(String value){
        this.value=value;
    }

    public String getValue(){
        return this.value;
    }

    public abstract String toLocalString();
}

public class Test {

    public static void main(String[] args) {

        System.out.println(Grade.A);
        System.out.println(Grade.A.getValue());
        System.out.println(Grade.A.toLocalString());
        System.out.println(Grade.B);
        System.out.println(Grade.B.getValue());
        System.out.println(Grade.B.toLocalString());
        System.out.println(Grade.C);
        System.out.println(Grade.C.getValue());
        System.out.println(Grade.C.toLocalString());
        System.out.println(Grade.D);
        System.out.println(Grade.D.getValue());
        System.out.println(Grade.D.toLocalString());

    }

}

结果：

　　A 81-100 优 B 71-80 良 C 61-70 中 D 0-60 差