Java 枚举

好久不写博客了，回忆回忆一下Java枚举

> enum 关键字来定义，各个常量使用逗号 , 来分割

package cn.tina.enums;

import java.util.Arrays;

/**
 * 根据不同日期查询数据拼接SQL
 *
 * @author Tina
 * @version 1.0
 * @since 2022/1/24 22:45
 **/
public enum Growth {
    TODAY("today", "and TO_CHAR(LOGIN_TIME,'YYYY-MM-DD')=TO_CHAR(SYSDATE,'YYYY-MM-DD')"),
    YESTERDAY("yesterday", "and TO_CHAR(LOGIN_TIME,'YYYY-MM-DD')=TO_CHAR(SYSDATE-1,'YYYY-MM-DD')"),
    THISWEEK("thisWeek", "and LOGIN_TIME >= TRUNC(NEXT_DAY(SYSDATE-8,1)+1) AND LOGIN_TIME < TRUNC(NEXT_DAY(SYSDATE-8,1)+7)+1"),
    LASTWEEK("lastWeek", "and LOGIN_TIME >= TRUNC(NEXT_DAY(SYSDATE-8,1)-6) AND LOGIN_TIME < TRUNC(NEXT_DAY(SYSDATE-8,1)+1)"),
    THISMONTH("thisMonth", "and TO_CHAR(LOGIN_TIME,'YYYY-MM')=TO_CHAR(SYSDATE,'YYYY-MM')"),
    LASTMONTH("lastMonth", "and TO_CHAR(LOGIN_TIME,'YYYY-MM')=TO_CHAR(ADD_MONTHS(SYSDATE,-1),'YYYY-MM')"),
    UNKNOWN("error", "and 1=1"),
    ALL("all", "and 1=1");
    private String key;
    private String sql;

    Growth(String key, String sql) {
        this.key = key;
        this.sql = sql;
    }

    public String getKey() {
        return key;
    }

    public void setKey(String key) {
        this.key = key;
    }

    public String getSql() {
        return sql;
    }

    public void setSql(String sql) {
        this.sql = sql;
    }

    /**
     * 根据Key得到枚举的Value
     * 普通for循环遍历，比较判断
     *
     * @param key
     * @return
     */
    public static Growth getEnumType(String key) {
        Growth[] Growths = Growth.values();
        for (int i = 0; i < Growths.length; i++) {
            if (Growths[i].getKey().equals(key)) {
                return Growths[i];
            }
        }
        return Growth.UNKNOWN;
    }

    /**
     * 根据Key得到枚举的Value
     * 增强for循环遍历，比较判断
     *
     * @param key
     * @return
     */
    public static Growth getEnumType1(String key) {
        Growth[] Growths = Growth.values();
        for (Growth Growth : Growths) {
            if (Growth.getKey().equals(key)) {
                return Growth;
            }
        }
        return Growth.UNKNOWN;
    }

    /**
     * 根据Key得到枚举的Value
     * Lambda表达式，比较判断（JDK 1.8）
     *
     * @param key
     * @return
     */
    public static Growth getEnumType2(String key) {
        Growth[] Growths = Growth.values();
        Growth result = Arrays.asList(Growths).stream()
            .filter(Growth -> Growth.getKey().equals(key))
            .findFirst().orElse(Growth.UNKNOWN);

        return result;
    }

    /**
     * 根据Key得到枚举的Value
     * Lambda表达式，比较判断（JDK 1.8）
     *
     * @param key
     * @return
     */
    public static Growth getEnumType3(String key) {
        return Arrays.asList(Growth.values()).stream()
            .filter(Growth -> Growth.getKey().equals(key))
            .findFirst().orElse(Growth.UNKNOWN);
    }

    @Override
    public String toString() {
        return "Growth{" +
            "key='" + key + '\'' +
            ", sql='" + sql + '\'' +
            '}';
    }
}

​注意一下：toString 需要重写​