讲述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
复制代码 代码如下: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,所以它具有的.属性和方法。遍历枚举:
复制代码 代码如下:public class Main {
public static void main(String[] args) {
for(Day day:es()) {
tln(day);
}
}
}
3. 枚举可以带字段和方法,以下示例来自官方The Java Tutorials
复制代码 代码如下: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();
}
}
以下现实中的示例来自官方的Java Tutorial:
复制代码 代码如下: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. 枚举是singleton,可以用枚举来构建一个Singleton
复制代码 代码如下: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);
}
}