Introduction to how to use enumerations in Java

This article mainly introduces the use of Java enumeration in detail, which has certain reference value. Interested friends can refer to it

In actual programming, there are often such situations "Data set", their values ​​are stable in the program, and the elements in the "data set" are limited.

For example, seven data elements from Monday to Sunday make up the "data set" of the week, and four data elements of spring, summer, autumn and winter make up the "data set" of the four seasons.

How to better use these "data sets" in java? Therefore, enumerations come in handy. The following code details the use of enumerations.

package com.ljq.test;

/**
 * 枚举用法详解
 * 
 * @author jiqinlin
 * 
 */
public class TestEnum {
  /**
   * 普通枚举
   * 
   * @author jiqinlin
   *
   */
  public enum ColorEnum {
    red, green, yellow, blue;
  }

  /**
   * 枚举像普通的类一样可以添加属性和方法，可以为它添加静态和非静态的属性或方法
   * 
   * @author jiqinlin
   *
   */
  public enum SeasonEnum {
    //注：枚举写在最前面，否则编译出错
    spring, summer, autumn, winter;

    private final static String position = "test";

    public static SeasonEnum getSeason() {
      if ("test".equals(position))
        return spring;
      else
        return winter;
    }
  }

  /**
   * 性别
   * 
   * 实现带有构造器的枚举
   * 
   * @author jiqinlin Java学习交流QQ群：589809992 我们一起学Java！
   *
   */
  public enum Gender{
    //通过括号赋值,而且必须带有一个参构造器和一个属性跟方法，否则编译出错
    //赋值必须都赋值或都不赋值，不能一部分赋值一部分不赋值；如果不赋值则不能写构造器，赋值编译也出错
    MAN("MAN"), WOMEN("WOMEN");

    private final String value;

    //构造器默认也只能是private, 从而保证构造函数只能在内部使用
    Gender(String value) {
      this.value = value;
    }

    public String getValue() {
      return value;
    }
  }

  /**
  * 订单状态
  * 
  * 实现带有抽象方法的枚举
  * 
  * @author jiqinlin
  *
  */
  public enum OrderState {
    /** 已取消 */
    CANCEL {public String getName(){return "已取消";}},
    /** 待审核 */
    WAITCONFIRM {public String getName(){return "待审核";}},
    /** 等待付款 */
    WAITPAYMENT {public String getName(){return "等待付款";}},
    /** 正在配货 */
    ADMEASUREPRODUCT {public String getName(){return "正在配货";}},
    /** 等待发货 */
    WAITDELIVER {public String getName(){return "等待发货";}},
    /** 已发货 */
    DELIVERED {public String getName(){return "已发货";}},
    /** 已收货 */
    RECEIVED {public String getName(){return "已收货";}};

    public abstract String getName();
  }

  public static void main(String[] args) {
    //枚举是一种类型，用于定义变量，以限制变量的赋值；赋值时通过“枚举名.值”取得枚举中的值
    ColorEnum colorEnum = ColorEnum.blue;
    switch (colorEnum) {
    case red:
      System.out.println("color is red");
      break;
    case green:
      System.out.println("color is green");
      break;
    case yellow:
      System.out.println("color is yellow");
      break;
    case blue:
      System.out.println("color is blue");
      break;
    }

    //遍历枚举
    System.out.println("遍历ColorEnum枚举中的值");
    for(ColorEnum color : ColorEnum.values()){
      System.out.println(color);
    }

    //获取枚举的个数
    System.out.println("ColorEnum枚举中的值有"+ColorEnum.values().length+"个");

    //获取枚举的索引位置，默认从0开始
    System.out.println(ColorEnum.red.ordinal());//0
    System.out.println(ColorEnum.green.ordinal());//1
    System.out.println(ColorEnum.yellow.ordinal());//2
    System.out.println(ColorEnum.blue.ordinal());//3

    //枚举默认实现了java.lang.Comparable接口
    System.out.println(ColorEnum.red.compareTo(ColorEnum.green));//-1

    //--------------------------
    System.out.println("===========");
    System.err.println("季节为" + SeasonEnum.getSeason());


    //--------------
    System.out.println("===========");
    for(Gender gender : Gender.values()){
      System.out.println(gender.value);
    }

    //--------------
    System.out.println("===========");
    for(OrderState order : OrderState.values()){
      System.out.println(order.getName());
    }
  }
}

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