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本文實(shí)例講述了java中enum的用法。分享給大家供大家參考。具體分析如下：

1. 基本用法

	enum Day {

	    SUNDAY, MONDAY, TUESDAY, WENDSDAY, THURSDAY, FRIDAY, SATURDAY;

	}

枚舉是常量，所以應(yīng)該用大寫。

2. 枚舉是對象

枚舉隱含地繼承了java.lang.Enum，所以它具有java.lang.Enum的屬性和方法。遍歷枚舉：

復(fù)制代碼代碼如下:

	public class Main {

	    public static void main(String[] args) {

	        for(Day day:Day.values()) {

	            System.out.println(day);

	        }

	    }

	}

3. 枚舉可以帶字段和方法，以下示例來自官方The Java™ Tutorials

復(fù)制代碼代碼如下:

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();
    }
}

以下現(xiàn)實(shí)中的示例來自官方的Java Tutorial:

復(fù)制代碼代碼如下:

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. 枚舉是singleton，可以用枚舉來構(gòu)建一個Singleton

復(fù)制代碼代碼如下:

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);
    }
}

希望本文所述對大家的Java程序設(shè)計有所幫助。