Java Enum 枚举用法 遍历枚举 获取枚举对象

一、创建一个枚举对象

        1、代码如下：

 
import java.util.Arrays;
import java.util.Iterator;
import java.util.Optional;
 
/**
 * Description: 异常类型枚举
 * @author w
 * @version 1.0
 * @date 2022/8/1 19:47
 */
public enum ExpEnum {
 
    PWD_ERROR("5001","密码错误"),
 
    INNER_ERROR("5002","内部错误"),
 
    OTHER_ERROR("5005","其他错误");
 
    private String code ;
    private String msg ;
 
    ExpEnum(String code, String msg) {
        this.code = code;
        this.msg = msg;
    }
 
    public String getCode() {
        return code;
    }
 
    public void setCode(String code) {
        this.code = code;
    }
 
    public String getMsg() {
        return msg;
    }
 
    public void setMsg(String msg) {
        this.msg = msg;
    }
 
    /**@Description: 根据code获取枚举对象
     * @param code
     * @return
     * @version v1.0
     * @author wu
     * @date 2022/8/1 20:28
     */
    public static ExpEnum get(String code){
        Iterator iterator = Arrays.stream(ExpEnum.values()).iterator();
        while (iterator.hasNext()){
            ExpEnum next = iterator.next();
            if(next.code.equals(code)){
                return next ;
            }
        }
        return null;
    }
 
    /**@Description: 根据code获取枚举对象 --- Java8方式
     * @param
     * @return
     * @version v1.0
     * @author wu
     * @date 2022/8/1 20:30
     */
    public static ExpEnum getByJava8(String code){
        Optional first = Arrays.stream(ExpEnum.values()).filter(e -> e.code.equals(code)).findFirst();
//        ExpEnum expEnum = first.get();
        ExpEnum expEnum = first.orElse(null);
        return expEnum;
    }
}

二、测试

        1、遍历枚举、获取枚举对象的值

 /**@Description: 遍历枚举
     * @return
     * @version v1.0
     * @author wu
     * @date 2022/8/1 20:32
     */
    @Test
    public void forEachTest(){
        ExpEnum[] values = ExpEnum.values();
        for (ExpEnum e : values) {
            System.out.println(e.ordinal() + ",name :"+ e.name()+ ",code:"+e.getCode() +", msg:"+e.getMsg() );
        }
    }
 
    /**@Description: 获取枚举对象
     * @version v1.0
     * @author wu
     * @date 2022/8/1 20:35
     */
    @Test
    public void getTest(){
        ExpEnum expEnum = ExpEnum.get("5001");
        System.out.println(expEnum);
    }
 
    /**@Description: 获取枚举对象 --- Java8
     * @version v1.0
     * @author wu
     * @date 2022/8/1 20:37
     */
    @Test
    public void getByJava8Test(){
        ExpEnum byJava8 = ExpEnum.getByJava8("5002");
        System.out.println(byJava8);
    }

三、使用枚举简化多个if else        

        1、原代码情况

public String process(String code){
        String res = null ;
        if("1".equals(code)){
            res = "状态一 if";
        }else if("2".equals(code)){
            res = "状态二 if";
        }else if("3".equals(code)){
            res = "状态三 if";
        }else if("4".equals(code)){
            res = "状态四 if";
        }
        return  res;
    }

        2、使用枚举Enum简化，代码如下：

    public String process2(String code){
        return Status.get(code).msg;
    }
 
    static enum Status {
 
        ONE("1","状态一"),
        TWO("2","状态二"),
        THREE("3","状态三"),
        FOUR("4","状态四");
 
        private String code ;
        private String msg;
 
        Status(String code, String msg) {
            this.code = code;
            this.msg = msg;
        }
 
        public String getCode() {
            return code;
        }
 
        public void setCode(String code) {
            this.code = code;
        }
 
        public String getMsg() {
            return msg;
        }
 
        public void setMsg(String msg) {
            this.msg = msg;
        }
 
        public static Status get(String code){
            Status status = Arrays.stream(Status.values()).filter(e -> e.getCode().equals(code)).findFirst().orElse(null);
            return status;
        }
    }