【JAVA学习笔记】43

【JAVA学习笔记】43 - 枚举类

项目代码

https://github.com/yinhai1114/Java_Learning_Code/tree/main/IDEA_Chapter11/src/com/yinhai/enum_

〇、创建时自动填入版权作者等信息

如何在每个文件创建的时候打入自己的信息以及版权呢

菜单栏-File-setting-Editor-File and Code Templaters -Includes-输入信息如下图

一、引出

要求创建季节（Season）对象，请设计并完成

/*** @author 银海* @version 1.0*/
public class Enumeration01 {public static void main(String[] args) {Season season = new Season("spring", "worm");Season season1 = new Season("winter", "cold");Season season2 = new Season("summer", "hot");Season season3 = new Season("autumn", "cold");//对于季节而言，是固定的四个 不会有更多//因此这样设计不好，所以引出枚举类，把对象一个个列举出来Season other = new Season("asdasdas", "~~~~~~~~~");}
}
class Season{private String name;private String desc;public Season(String name, String desc) {this.name = name;this.desc = desc;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDesc() {return desc;}public void setDesc(String desc) {this.desc = desc;}
}

二、两种实现方式

1.自定义类实现枚举

1)不需要提供setXxx方法，因为枚举对象值通常为只读.

2)对枚举对象/属性使用final + static 共同修饰，实现底层优化.

3)枚举对象名通常使用全部大写，常量的命名规范

4)枚举对象根据需要，也可以有多个属性

public class Enumeration02 {public static void main(String[] args) {System.out.println(Season.AUTUMN);System.out.println(Season.SPRING);System.out.println(Season.SUMMER);System.out.println(Season.WINTER);}
}class Season {private String name;private String desc;//3.在Season内部直接创建对象，加上public static//4.优化可以加入final修饰符public final static Season SPRING = new Season("春天", "暖");public final static Season WINTER = new Season("冬天", "寒冷");public final static Season AUTUMN = new Season("秋天", "冷");public final static Season SUMMER = new Season("夏天", "热");//1.私有化构造器public Season(String name, String desc) {this.name = name;this.desc = desc;}//2.去掉set方法 防止被修改public String getName() {return name;}public String getDesc() {return desc;}}

小结：进行自定义类实现枚举有如下特点

1)构造器私有化

2)本类内部创建一组对象

3)对外暴露对象(通过为对象添加public final static修饰符)

4)可以提供get方法，但是不要提供set

2.enum关键字实现枚举（引出）

public class Enumeration03 {public static void main(String[] args) {System.out.println(Season.AUTUMN);System.out.println(Season.SPRING);System.out.println(Season.SUMMER);System.out.println(Season.WINTER);}}
enum Season {//1.使用enum代替class//2.//常量名(实参列表);//3.如果有多个常量(对象)SPRING("春天", "暖"),WINTER("冬天", "寒冷"),AUTUMN("秋天", "冷"),SUMMER("夏天", "热");//等价于自定义的public final static Season SPRING = new Season("春天", "暖");//4.如果使用enum来实现枚举，要求将常量对象写在前面private String name;private String desc;private Season(String name, String desc) {this.name = name;this.desc = desc;}public String getName() {return name;}public String getDesc() {return desc;}}