java枚举类型enum的使用实例,以及java程序中常量有什么用?
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问:枚举有有什么用?
答:定义常量,作用和jfinal一样,用来定义固定值的变量,即常量变量。
java程序,为什么要定义常量,常量有什么用?
引入常量,是为了:
1)直接调用即可,不用每次都输入“telNum”。
2)便于代码的可读性,如果你在程序中输入“telNum”别人不明白是什么,你固定写到某个位置,大家一看就明白了。
3)也方便查看,常量就像是一个数据字典(0是待提交 1已提交 2已审核等等)一样,各数值代表什么意思,一目了然。
5)也可以防止别写程序时将“telNum”敲错,因为使用"对象名.成员变量名"输入“.”的时候会有可能代码提示,选择即可,这样是不可能出错的。
6)增加程序的可读性,可维护性,如果直接在代码中写入Db.set("current_status","1");没有人会明白,如果将这些状态位通过变量在某个类中通过jfinal 进行维护或者在枚举类中维护,程序只是调取Db.set("current_status",CurrentStatus.CURRENT_STATUS_0);即可。
如jf工程中,如下的用法
public class ProjectContants {public static String CURRENT_USER = "CURRENT_USER";public static String CURRENT_ORGAN = "CURRENT_ORGAN";public static String CURRENT_PROJECT = "CURRENT_PROJECT";public static String RANDOM_IMAGE_CODE="RANDOM_IMAGE_CODE";}
总结:
所以,变量最大的用处就是为了消除,java程序中,“某些状态位,外人完全不明白什么意思,”
如下:
==================================java枚举类型enum的使用实例==================================
http://blog.csdn.net/ahgaojie451/article/details/45362053
Java枚举类型enum的使用
java中定义常量有两种方法:final关键字和enum枚举。Java中的枚举类型采用关键字enum来定义,从jdk1.5才有的新类型,所有的枚举类型都是继承自Enum类型。要了解枚举类型,建议大家先打开jdk中的Enum类简单读一下,这个类里面定义了很多protected方法,比如构造函数,如果要使用这些方法我们可以把枚举类型定义到当前类中。每个枚举类型,都有自己的名字和顺序,当我们输出一个枚举类型的时候,会输入枚举类型的name,具体可以参考下面的例子。
- public enum OperationType {
-
- ADD_KEYWORD("add_keyword@resource", "KEYWORD"),
- ADD_START_KEYWORD("add_start_keyword@resource", "KEYWORD"),
- ADD_STOP_KEYWORD("add_stop_keyword@resource", "KEYWORD"),
- DELETE_KEYWORD("delete_keyword@resource", "KEYWORD"),
- ADD_REC_TO_RECYCLE("add_rec_to_recycle@resource", "KEYWORD"),
- STOP_KEYWORD("stop_keyword@resource", "KEYWORD"),
- STOP_ALL_KEYWORD("stop_all_keyword@resource", "KEYWORD"),
- START_KEYWORD("start_keyword@resource", "KEYWORD"),
- START_ALL_KEYWORD("start_all_keyword@resource", "KEYWORD"),
- BID_KEYWORD("bid_keyword@resource", "KEYWORD"),
- MODIFY_BID_KEYWORD("modify_bid_keyword@resource", "KEYWORD"),
- MODIFY_ADD_KEYWORD("modify_add_keyword@resource", "KEYWORD"),
- MODIFY_SUB_KEYWORD("modify_sub_keyword@resource", "KEYWORD"),
- MODIFY_KEYWORD_TAG("modify_keyword_tag@resource", "KEYWORD"),
- CANCEL_KEYWORD_TAG("cancel_keyword_tag@resource", "KEYWORD"),
- SET_PREFERENTIAL_PRODUCT("set_preferential_product@resource", "KEYWORD"),
- CANCEL_PREFERENTIAL_PRODUCT("cancel_preferential_product@resource", "KEYWORD"),
- SET_ADMATCH("set_admatch@resource", "KEYWORD"),
- CANCEL_ADMATCH("cancel_admatch@resource", "KEYWORD"),
- MODIFY_COST_LIMIT("modify_cost_limit@resource", "ACCOUNT"),
- MODIFY_BALANCE_ALERT_AMOUNT("modify_balance_alert_amount@resource", "ACCOUNT"),
- MODIFY_BALANCE_ALERT_EMAIL("modify_balance_alert_email@resource", "ACCOUNT"),
- MODIFY_BALANCE_ALERT_PHONE("modify_balance_alert_phone@resource", "ACCOUNT"),
- ACCEPT_AGREEMENT("accept_agreement@resource", "ACCOUNT"),
- START_ACCOUNTS_TATUS("start_account_status@resource", "ACCOUNT"),
- STOP_ACCOUNT_STATUS("stop_account_status@resource", "ACCOUNT"),
- SETTING_ACCOUNT_LANGUAGE("setting_account_language@resource", "ACCOUNT"),
- CANCEL_ACCOUNT_LANGUAGE("cancel_account_language@resource", "ACCOUNT"),
- ALLOW_RECOMMEND_KEYWORD("allow_recommend_keyword@resource", "ACCOUNT"),
- DONT_ALLOW_RECOMMEND_KEYWORD("dont_allow_recommend_keyword@resource", "ACCOUNT"),
- UNFREEZE_CUST("unfreeze_cust@resource", "ACCOUNT"),
- ADD_OFFER("add_offer@resource", "PRODUCT"),
- CLEAN_PRODUCT("clean_product@resource", "PRODUCT"),
- DELETE_OFFER("delete_offer@resource", "PRODUCT"),
- ADD_ALL_OFFER("add_all_offer@resource", "PRODUCT"),
- DELETE_ALL_OFFER("delete_all_offer@resource", "PRODUCT"),
- ADD_BEST_MATCH_OFFER("add_best_match_offer@resource", "PRODUCT"),
- CREAT_TAG("create_tag@resource", "TAG"),
- MODIFY_TAG_NAME("modify_tag_name@resource", "TAG"),
- DELETE_TAG("delete_tag@resource", "TAG"),
- INSERT_AUTH_MANAGE("insert_authority@resource", "AUTHORITY"),
- MODIFY_AUTH_MANAGE("modify_authority@resource", "AUTHORITY"),
- CANCEL_AUTH_MANAGE("cancel_authority@resource", "AUTHORITY"),
- START_QUICK_PROMOTION("start_quick_promotion@resource", "QUICKPRROMOTION"),
- STOP_QUICK_PROMOTION("stop_quick_promotion@resource", "QUICKPRROMOTION"),
- UPDATE_QUICK_PRICE("update_quick_price@resource", "QUICKPRROMOTION"),
-
- private OperationType(String resourceKey, String type) {
- this.resourceKey = resourceKey;
- this.type = type;
- }
-
- private final String resourceKey;
- private final String type;
-
- public String getResourceKey() {
- return resourceKey;
- }
-
- public String getType() {
- return type;
- }
-
- public static OperationType getOperationType(String name) {
- return OperationType.valueOf(name);
- }
-
- }
上面定义了一个java枚举类型的类,构造函数的两个参数很重要,分别对应枚举实例的两个参数。下面的测试代码,可以明确告诉你如何使用java枚举获取对应的信息。
- public class Test {
- public static void main(String[] args) {
- OperationType operationType = OperationType.getOperationType("ADD_STOP_KEYWORD");
- System.out.println("operationType.getType():" + operationType.getType());
- System.out.println("operationType.getResourceKey():" + operationType.getResourceKey());
- }
- }
上例的输出结果如下:
- <strong>operationType.getType():KEYWORD
- operationType.getResourceKey():add_stop_keyword@resource</strong>
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