【JAVA学习笔记】43

【JAVA学习笔记】43 - 枚举类

news2024/10/1 12:25:59

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;
    }

}