如何使用Java Enum

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====>MondayTue====>TuesdayWed====>WednesdayThu====>ThursdayFri====>FridaySat====>SaturdaySun====>SundayFri

1. 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());    }}