简单的用法：JavaEnum简单的用法一般用于代表一组常用常量，可用来代表一类相同类型的常量值。如：
性别：
public enum SexEnum { male, female; } 颜色：
public enum Color { RED, BLUE,GREEN,BLACK; }
枚举对象里面的值都必须是唯一的。
可以通过Enum类型名直接引用该常量，如SexEnum.male,Color.RED.
复杂用法：Java为枚举类型提供了一些内置的方法，同事枚举常量还可以有自己的方法。可以很方便的遍历枚举对象，看个下面的例子：
1. 代码一 WeekDay.java: public enum WeekDay { Mon("Monday"), Tue("Tuesday"), Wed("Wednesday"), Thu("Thursday"), Fri( "Friday"), Sat("Saturday"), Sun("Sunday"); private final String day; private WeekDay(String day) { this.day = day; } public static void printDay(int i){ switch(i){ case 1: System.out.println(WeekDay.Mon); break; case 2: System.out.println(WeekDay.Tue);break; case 3: System.out.println(WeekDay.Wed);break; case 4: System.out.println(WeekDay.Thu);break; case 5: System.out.println(WeekDay.Fri);break; case 6: System.out.println(WeekDay.Sat);break; case 7: System.out.println(WeekDay.Sun);break; default:System.out.println("wrong number!"); } } public String getDay() { return day;
}
}
1. 代码二 WeekDayTest.java:
public class WeekDayTest {
public static void main(String args[]) {
for (WeekDay day : WeekDay.values()) {
System.out.println(day + "====>" + day.getDay());
}
WeekDay.printDay(5);
}
}
输出结果为：
Mon====>Monday
Tue====>Tuesday
Wed====>Wednesday
Thu====>Thursday
Fri====>Friday
Sat====>Saturday
Sun====>Sunday
Fri
2.Java Enum原理
Java Enum类型的语法结构尽管和java类的语法不一样，应该说差别比较大。但是经过编译器编译之后产生的是一个class文件。该class文件经过反编译可以看到实际上是生成了一个类，该类继承了java.lang.Enum.
WeekDay经过反编译(javap WeekDay命令)之后得到的内容如下(去掉了汇编代码)：
public final class WeekDay extends java.lang.Enum{
public static final WeekDay Mon;
public static final WeekDay Tue;
public static final WeekDay Wed;
public static final WeekDay Thu;
public static final WeekDay Fri;
public static final WeekDay Sat;
public static final WeekDay Sun;
static {};
public static void printDay(int);
public java.lang.String getDay();
public static WeekDay[] values();
public static WeekDay valueOf(java.lang.String);
}
所以实际上Enum类型就是以Java类来实现的，没有什么新的特点，只不过java编译器帮我们做了语法的解析和编译。完全也可以自己实现。但是既然有这样方便一个东西，当然会去用了。
使用实例：
1》：以Class定义的
public class PCUEnum {
public static void main(String[] args) {
System.out
.println(PCUEnum.TaskStatus.get(PCUEnum.TaskStatus.DELETED));
}
public enum TaskStatus {
// 1:等待执行 2:正在执行 3:执行完毕 4:执行失败 5:暂停 100:已经删除 101:已经送审
NOTINQUEUE,WAITING, EXECUTING, EXECUTED, FAILED, SUSPEND, DELETED,WAITING_AUDIT;
public static int get(TaskStatus s) {
int result = 0;
switch (s) {
case NOTINQUEUE:
result=0;
break;
case WAITING:
result = 1;
break;
case EXECUTING:
result = 2;
break;
case EXECUTED:
result = 3;
break;
case FAILED:
result = 4;
break;
case SUSPEND:
result = 5;
break;
case DELETED:
result = 100;
break;
case WAITING_AUDIT:
result = 101;
break;
}
return result;
}
}
}
1.1》：以类为实例：
public class EnumClass {
enum explore {
HERE, THERE
}
enum WeekDay {
Mon("Monday"), Tue("Tuesday"), Wed("Wednesday"), Thu("Thursday"), Fri("Friday"), Sat("Saturday"),
Sun("Sunday"), Wro("Wrong day");
private String day;
WeekDay(String day){
this.day = day;
}
public String getDay() {
return day;
}
}
public static void main(String[] args) {
System.out.println(EnumClass.explore.HERE);
System.out.println("--------");
for(EnumClass.WeekDay day : EnumClass.WeekDay.values()) {
System.out.println(day.getDay());
}
}
}
2》：以Enum定义的
package com.zhou.test;
public enum TaskEnumStatus {
NOTINQUEUE(1),WAITING(2), EXECUTING(3), EXECUTED(4), FAILED(5), SUSPEND(6), DELETED(7),WAITING_AUDIT(8);
private int i;
private TaskEnumStatus(int i) {
this.i = i;
}
public int getEnumStatus() {
return i;
}
}
public static void main(String[] args) {
System.out.println(TaskEnumStatus.NOTINQUEUE + "=" + TaskEnumStatus.NOTINQUEUE.getEnumStatus());
}
2.1》：以Enum定义
public enum UserStatusEnum {
DISABLE("disable"),
ENABLE("enable");
private String value;
UserStatusEnum(String value){
this.value = value;
}
public String getValue() {
return value;
}
public String toString() {
return value;
}
public static void main(String[] args) {
System.out.println(UserStatusEnum.DISABLE);
}
}
2.2》：以Enum定义
public enum NumberEnum {
CONST_FOUR(4), CONST_ENIGHT(8), CONST_NINE(999999);
private final int value;
NumberEnum(int value) {
this.value = value;
}
public int getValue() {
return value;
}
public static void main(String[] args) {
System.out.println(NumberEnum.CONST_ENIGHT.getValue());
}
}
