講述java中enum的用法

本文實例講述了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

複製代碼 代碼如下:enum Day {

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

}

枚舉是常量，所以應該用大寫。

　　2. 枚舉是對象

枚舉隱含地繼承了，所以它具有的.屬性和方法。遍歷枚舉：

複製代碼 代碼如下:public class Main {

public static void main(String[] args) {

for(Day day:es()) {

tln(day);

}

}

}

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

複製代碼 代碼如下:public enum EnumDemo {

AOBJECT("field one", "field two");

private String field1;

private String field2;

EnumDemo(String val1, String val2){

d1 = val1;

d2 = val2;

}

public void printFields(){

tln(d1);

tln(d2);

}

public static void main(String[] args) {

tFields();

}

}

以下現實中的示例來自官方的Java Tutorial:

複製代碼 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) {

= mass;

us = 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: es()){

tln(aceGravity());

tln(aceWeight(earthWeight/aceGravity()));

}

}

}

　　4. 枚舉是singleton，可以用枚舉來構建一個Singleton

複製代碼 代碼如下:public enum Singleton {

INSTANCE(new String[]{"arg1", "arg2"});

String[] myArgs;

Singleton(String[] args){

gs = args;

}

public static Singleton getInstance(){

return INSTANCE;

}

public static void main(String[] args) {

for(String arg : gs)

tln(arg);

}

}