簡單的用法：JavaEnum簡單的用法一般用于代表一組常用常量，可用來代表一類相同類型的常量值。如：

性別： public enum SexEnum {male, female;}顏色： public enum Color {RED, BLUE,GREEN,BLACK;}

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枚舉對(duì)象里面的值都必須是唯一的。

可以通過Enum類型名直接引用該常量，如SexEnum.male,Color.RED.

復(fù)雜用法：Java為枚舉類型提供了一些內(nèi)置的方法，同事枚舉常量還可以有自己的方法。可以很方便的遍歷枚舉對(duì)象，看個(gè)下面的例子：

1. 代碼一 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;} }

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1. 代碼二 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);}}輸出結(jié)果為：Mon====>MondayTue====>TuesdayWed====>WednesdayThu====>ThursdayFri====>FridaySat====>SaturdaySun====>SundayFri

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?2.Java Enum原理
Java Enum類型的語法結(jié)構(gòu)盡管和java類的語法不一樣，應(yīng)該說差別比較大。但是經(jīng)過編譯器編譯之后產(chǎn)生的是一個(gè)class文件。該class文件經(jīng)過反編譯可以看到實(shí)際上是生成了一個(gè)類，該類繼承了java.lang.Enum.

WeekDay經(jīng)過反編譯(javap WeekDay命令)之后得到的內(nèi)容如下(去掉了匯編代碼)：

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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);}

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所以實(shí)際上Enum類型就是以Java類來實(shí)現(xiàn)的，沒有什么新的特點(diǎn)，只不過java編譯器幫我們做了語法的解析和編譯。完全也可以自己實(shí)現(xiàn)。但是既然有這樣方便一個(gè)東西，當(dāng)然會(huì)去用了。

使用實(shí)例：
1》：以Class定義的

public class PCUEnum {public static void main(String[] args) {System.out.println(PCUEnum.TaskStatus.get(PCUEnum.TaskStatus.DELETED));}public enum TaskStatus {// 1:等待執(zhí)行 2:正在執(zhí)行 3:執(zhí)行完畢 4:執(zhí)行失敗 5:暫停 100:已經(jīng)刪除 101:已經(jīng)送審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;}}}

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?1.1》：以類為實(shí)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());}} }

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?2》：以Enum定義的

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());}

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?2.1》：以Enum定義

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);} }

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?2.2》：以Enum定義

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());} }

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轉(zhuǎn)載于:https://www.cnblogs.com/MaxElephant/p/8086743.html

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