java中enum的用法

本文实例讲述了java中enum的用法。分享给大家供大家参考。具体分析如下：

1. 基本用法

enum day {
    sunday, monday, tuesday, wendsday, thursday, friday, saturday;
}

枚举是常量，所以应该用大写。

2. 枚举是对象

枚举隐含地继承了java.lang.enum，所以它具有java.lang.enum的属性和方法。遍历枚举：

public class main {
    public static void main(string[] args) {
        for(day day:day.values()) {
            system.out.println(day);
        }
    }
}

3. 枚举可以带字段和方法，以下示例来自官方the java™ tutorials

public enum enumdemo {
    aobject("field one", "field two");

    private string field1;
    private string field2;

    enumdemo(string val1, string val2){
        this.field1 = val1;
        this.field2 = val2;
    }

    public void printfields(){
        system.out.println(this.field1);
        system.out.println(this.field2);
    }

    public static void main(string[] args) {
        enumdemo.aobject.printfields();
    }
}

以下现实中的示例来自官方的java tutorial:

public enum planet {
    mercury (3.303e+23, 2.4397e6),
    venus   (4.869e+24, 6.0518e6),
    earth   (5.976e+24, 6.37814e6),
    mars    (6.421e+23, 3.3972e6),
    jupiter (1.9e+27,   7.1492e7),
    saturn  (5.688e+26, 6.0268e7),
    uranus  (8.686e+25, 2.5559e7),
    neptune (1.024e+26, 2.4746e7);

    private final double mass;   // in kilograms
    private final double radius; // in meters

    planet(double mass, double radius) {
        this.mass = mass;
        this.radius = radius;
    }

    private double mass() { return mass; }
    private double radius() { return radius; }

    // universal gravitational constant  (m3 kg-1 s-2)
    public static final double g = 6.67300e-11;

    double surfacegravity() {
        return g * mass / (radius * radius);
    }

    double surfaceweight(double othermass) {
        return othermass * surfacegravity();
    }

    public static void main(string[] args) {
        double earthweight = 120;
        for(planet p: planet.values()){
            system.out.println(p.surfacegravity());
            system.out.println(p.surfaceweight(earthweight/earth.surfacegravity()));
        }
    }
}

4. 枚举是singleton，可以用枚举来构建一个singleton

public enum singleton {
    instance(new string[]{"arg1", "arg2"});

    string[] myargs;
    singleton(string[] args){
        this.myargs = args;
    }

    public static singleton getinstance(){
        return instance;
    }

    public static void main(string[] args) {
        for(string arg : instance.myargs)
            system.out.println(arg);
    }
}

希望本文所述对大家的java程序设计有所帮助。