阿里p9三分钟教你Java 自定义可继承枚举Enum的案例

古城微笑少年丶 2022-10-22 09:09 174阅读 0赞

**这篇文章主要介绍了java 自定义可继承枚举Enum的案例，具有很好的参考价值，希望对大家有所帮助。一起跟随小编过来看看吧**

**一、定义enum抽象类**

public class AbstractEnum {
         
     private static final Map<String, AbstractEnum> nameEnumMap = new ConcurrentHashMap<>(); 
     @Getter
     protected String name; 
     protected AbstractEnum () {
        
     }
      
     protected AbstractEnum(String name) {
        
      this.name = name;
      if (!nameEnumMap.containsKey(name)) {
        
       nameEnumMap.put(name, this);
      }
     }
      
     public boolean equals(AbstractEnum abstractEnum) {
        
      return this.name == null || abstractEnum == null ? false : this.name.equals(abstractEnum.getName());
     }
      
     public String toString() {
        
      return this.name;
     }
      
     public static AbstractEnum valueOf(String name) {
        
      if (name == null)
       throw new NullPointerException("Name is null");
      
      AbstractEnum result = nameEnumMap.get(name);
      if (result != null) {
        
       return result;
      }
      
      throw new IllegalArgumentException(
        "No enum constant exists, name is." + name);
     }
      
     public static void init() {
        
     }
      
    }

**二、实际继承enum，与enum使用方法一致**

public class TypeEnum extends AbstractEnum {
         
     private static final Map<String, TypeEnum> nameEnumMap = new ConcurrentHashMap<>(); 
     protected TypeEnum(String name) {
        
     super(name);
     if (!nameEnumMap.containsKey(name)) {
        
     nameEnumMap.put(name, this);
     }
     }
      
     public static TypeEnum valueOf(String name) {
        
     if (name == null)
     throw new NullPointerException("Name is null");
      
     TypeEnum result = nameEnumMap.get(name);
     if (result != null) {
        
     return result;
     }
      
     throw new IllegalArgumentException(
     "No enum constant exists, name is." + name);
     }
      
     public static final TypeEnum TYPE_ONE = new TypeEnum("TYPE_ONE");
    }

**三、可继续继承枚举，进行枚举分类。**  
补充：Java中自定义枚举（Enum）项的值,可设置为指定的值

**一、代码**

package base.lang;
    /**
     * ClassName: StateEnum 
     * @Description: TODO
     * @author fuming
     * @date 2016年11月27日
     */
    public enum StateEnum
    {
        
    //添加枚举的指定常量
    online(10),
    offline(20);
    //必须增加一个构造函数,变量,得到该变量的值
    private int mState=0;
    private StateEnum(int value)
    {
        
    mState=value;
    }
    /**
    * @return 枚举变量实际返回值
    */
     public int getState()
     {
        
     return mState;
     } 
    }

**二、示例**

//enum
    StateEnum orderState=StateEnum.offline;
    //orderState=StateEnum.online;
    System.out.println("state="+ orderState.getState());

**三、打印结果**

state=20  //测试正常

**以上为个人经验，希望能给大家一个参考，也希望大家多多支持小编。如有错误或未考虑完全的地方，望不吝赐教。**