枚举（enum）及应用

Java枚举是一个特殊的类，一般表示一组常量。每个常量用逗号隔开。

1、枚举的定义

例如：定义一个星期的枚举：（枚举中的个量都是常量因此用大写字母）

枚举：

public enum  Week {
    SUN,MON,TUES,WED,THUR,FRI,SAT
}

测试代码：

public class Test {
    public static void main(String[] args) {
        Week w1=Week.SUN;
        Week w2=Week.MON;
        Week w3=Week.TUES;
        Week w4=Week.WED;
        Week w5=Week.THUR;
        Week w6=Week.FRI;
        Week w7=Week.SAT;
        System.out.println(w1+"n"+w2+"n"+w3+"n"
                +w4+"n"+w5+"n"+w6);
    }
}

运行结果

SUN
MON
TUES
WED
THUR
FRI

2、内部类中使用枚举

public class Test2 {
    enum Week{
        SUN,MON,TUES,WED,THUR,FRI,SAT
    }
    public static void main(String[] args) {
        Week w1=Week.SUN;
        Week w2=Week.MON;
        Week w3=Week.TUES;
        Week w4=Week.WED;
        Week w5=Week.THUR;
        Week w6=Week.FRI;
        Week w7=Week.SAT;
        System.out.println(w1+"n"+w2+"n"+w3+"n"
                +w4+"n"+w5+"n"+w6);
    }
}

运行结果：

SUN
MON
TUES
WED
THUR
FRI

每个枚举都是通过class在内部类实现的，且所有的枚举都是公共静态常量。

2、枚举的迭代

使用增强for迭代：

public class Test2 {
    enum Week{
        SUN,MON,TUES,WED,THUR,FRI,SAT
    }
    public static void main(String[] args) {
       for (Week week:Week.values()){//增强for
           System.out.println(week);
       }
    }
}

运行结果：

SUN
MON
TUES
WED
THUR
FRI
SAT
 

3、switch中应用枚举

import java.util.Scanner;

public class Test2 {
    enum Week{
        SUN,MON,TUES,WED,THUR,FRI,SAT
    }
    public static void main(String[] args) {
        Scanner input=new Scanner(System.in);
        System.out.print("请输入你喜欢的日期：");
        String s=input.next();
        Week w=Week.valueOf(s);
        switch (w){
            case SUN:
                System.out.println("你喜欢星期日");
                break;
            case MON:
                System.out.println("你喜欢星期一");
                break;
            case TUES:
                System.out.println("你喜欢星期二");
                break;
            case WED:
                System.out.println("你喜欢星期三");
                break;
            case THUR:
                System.out.println("你喜欢星期四");
                break;
            case FRI:
                System.out.println("你喜欢星期五");
                break;
            case SAT:
                System.out.println("你喜欢星期六");
                break;
        }
    }
}

运行结果：

请输入你喜欢的日期：WED
你喜欢星期三