Enum

java定义新的类型的方式：类、接口、枚举

public enum Color{
  RED,
  GREEN,
  BLUE;
}

取出枚举的全部类容：

for(Color c:Color.values()){     //Color.values()表示得到全部枚举内容
  System.out.println(c);
}

c.ordinal() //编号
c.name()  //名字

类集对枚举的支持：EnumMap、EnumSet

package com.company;
import java.util.EnumMap;
import java.util.Map;
​
enum Color{
    RED,GREEN,BLUE;
}
​
public class Main {
​
    public static void main(String[] args) {
        Map<Color,String> demo = new EnumMap<Color, String>(Color.class);
        demo.put(Color.RED,"红");
        demo.put(Color.GREEN,"绿");
        demo.put(Color.BLUE,"蓝");
        System.out.println("/********输出全部内容***********/");
        for(Color c : Color.values()){
            System.out.println(c.name()+":"+demo.get(c));
        }
        System.out.println("/********输出全部key***********/");
        for(Color c : demo.keySet()){
            System.out.println(c);
        }
        System.out.println("/********输出全部values***********/");
        for(String c : demo.values()){
            System.out.println(c);
        }
    }
}

例子：

package com.company;
​
enum ResultCode{
    SUCCESS(0),
    UNKNOWN_ERROR(1),
    ILLEGAL_OP_ERROR(2),
    MISS_PARAM_ERROR(3),
    ILLEGAL_PARAM_ERROR(4),
    DUPLICATE_OP_ERROR(20),
    NOT_SUPPORT_OP_ERROR(30),
    TOO_MANY_RECORDS_ERROR(40),
    NO_ORIGIN_VOUCHER(401),
    NO_RETRY_ERROR(500),
    RETRY_LATER(600),
    THRIFT_PROTOCOL_EXCEPTION(1000);
​
    private final int value;
​
    private ResultCode(int value) {
        this.value = value;
    }
​
    /**
     * Get the integer value of this enum value, as defined in the Thrift IDL.
     */
    public int getValue() {
        return value;
    }
​
    /**
     * Find a the enum type by its integer value, as defined in the Thrift IDL.
     * @return null if the value is not found.
     */
    public static ResultCode findByValue(int value) {
        switch (value) {
            case 0:
                return SUCCESS;
            case 1:
                return UNKNOWN_ERROR;
            case 2:
                return ILLEGAL_OP_ERROR;
            case 3:
                return MISS_PARAM_ERROR;
            case 4:
                return ILLEGAL_PARAM_ERROR;
            case 20:
                return DUPLICATE_OP_ERROR;
            case 30:
                return NOT_SUPPORT_OP_ERROR;
            case 40:
                return TOO_MANY_RECORDS_ERROR;
            case 401:
                return NO_ORIGIN_VOUCHER;
            case 500:
                return NO_RETRY_ERROR;
            case 600:
                return RETRY_LATER;
            case 1000:
                return THRIFT_PROTOCOL_EXCEPTION;
            default:
                return null;
        }
    }
}
​
public class EnumSet {
    public static void main(String[] args){
        System.out.println(ResultCode.SUCCESS);         //输出SUCCESS
        System.out.println(ResultCode.NO_ORIGIN_VOUCHER.getValue());    //输出NO_ORIGIN_VOUCHER的值
        for(ResultCode x:ResultCode.values()){              //遍历枚举内容
            System.out.println(x.getValue());               //输出数值
            System.out.println(x);                          //输出
        }
        Integer i=0;
        System.out.println(i.getClass().getTypeName());
    }
}