1. Basic Concepts
1. When a class has only a limited number of objects, we call this class an enumeration class.
2. When you need to define a set of constants, it is strongly recommended to use an enumeration class
3, the implementation of the enumeration class
2. Custom enumeration class
package com.example.java;
/**
* 一、枚举类的使用
* 1、枚举类的理解：类的对象只有有限个，确定的。我们称此类为枚举类
* 2、当需要定义一组常量时，强烈建议使用枚举类
* 3、如果枚举类中只有一个对象、则可以作为单例模式的实现方式
*
* 二、如何定义枚举类
* 方式一：在jdk5.0之前,自定义枚举类
* 方式二：jdk5.0之后，可以使用enum关键字定义枚举类
*
* Author:
* DATE: 2022/4/2 22:42
*/
class seasonTest01 {
public static void main(String[] args) {
Season spring = Season.SPRING;
System.out.println(spring);
}
}
//自定义枚举类
class Season{
//声明Season对象的属性
private final String seasonName;
private final String seasonDesc;
//2、私有化类的构造器,并给对象属性赋值
private Season(String seasonName,String seasonDesc){
this.seasonName = seasonName;
this.seasonDesc = seasonDesc;
}
//3、提供当亲枚举类的多个对象
public static final Season SPRING = new Season("春天","吹暖花开");
public static final Season SUMMER = new Season("夏天","夏日炎炎");
public static final Season AUTUMN = new Season("秋天","秋高气爽");
public static final Season WINTER = new Season("冬天","冰天雪地");
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
@Override
public String toString() {
return "Season{" +
"seasonName='" + seasonName + '\'' +
", seasonDesc='" + seasonDesc + '\'' +
'}';
}
}
3. Use the enum keyword to define an enumeration class
package com.example.java;
/**
* 使用enum关键字定义枚举类
*
* Author:
* DATE: 2022/4/2 22:42
*/
public class SeasonTest02 {
public static void main(String[] args) {
Season2 spring = Season2.SPRING;
System.out.println(spring);
//说明：定义的枚举类默认继承与于java.long.Enum类
System.out.println(Season2.class.getSuperclass());//class java.lang.Enum
}
}
//使用enum关键字定义枚举类
enum Season2 {
//1、提供当前枚举类的对象，多个对象之间用逗号隔开，末尾的对象分号结束
SPRING("春天","吹暖花开"),
SUMMER("夏天","夏日炎炎"),
AUTUMN("秋天","秋高气爽"),
WINTER("冬天","冰天雪地");
//2、声明Season对象的属性
private final String seasonName;
private final String seasonDesc;
//3、私有化类的构造器,并给对象属性赋值
private Season2(String seasonName,String seasonDesc){
this.seasonName = seasonName;
this.seasonDesc = seasonDesc;
}
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
// @Override
// public String toString() {
// return "Season{" +
// "seasonName='" + seasonName + '\'' +
// ", seasonDesc='" + seasonDesc + '\'' +
// '}';
// }
}
4. The main method of enumeration class
4.1. Common methods of enumeration classes
package com.example.java;
/**
* 使用enum关键字定义枚举类
*
* Author: cui
* DATE: 2022/4/2 22:42
*/
public class SeasonTest02 {
public static void main(String[] args) {
//1、toString();
System.out.println("*************toString();**************");
Season2 spring = Season2.SPRING;
System.out.println(spring);
//2、values()
System.out.println("*************values()**************");
Season2[] values = Season2.values();
for (int i = 0; i < values.length; i++) {
System.out.println(values[i]);
}
//3、valueOf(String objName):返回枚举类中对象名是objName的对象
System.out.println("*************valueOf(String objName)**************");
Season2 winter = Season2.valueOf("WINTER");
System.out.println(winter);
}
}
//使用enum关键字定义枚举类
enum Season2 {
//1、提供当前枚举类的对象，多个对象之间用逗号隔开，末尾的对象分号结束
SPRING("春天","吹暖花开"),
SUMMER("夏天","夏日炎炎"),
AUTUMN("秋天","秋高气爽"),
WINTER("冬天","冰天雪地");
//2、声明Season对象的属性
private final String seasonName;
private final String seasonDesc;
//3、私有化类的构造器,并给对象属性赋值
private Season2(String seasonName,String seasonDesc){
this.seasonName = seasonName;
this.seasonDesc = seasonDesc;
}
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
// @Override
// public String toString() {
// return "Season{" +
// "seasonName='" + seasonName + '\'' +
// ", seasonDesc='" + seasonDesc + '\'' +
// '}';
// }
}
5. Enumeration class implements interface
package com.example.java;
import java.lang.ref.SoftReference;
import java.sql.SQLOutput;
/**
* 使用enum关键字定义枚举类
* 三、Enum类中的常用方法
* values()方法：返回枚举类型的对象数组，该方法可以很方便地遍历所有的枚举值
* valueOf(String str):可以把一个字符串转为对应的枚举类对象。要求字符串必须是枚举类对象
* toString():返回的是当前枚举类对象常量的名称
*
* 四、使用enum关键字定义枚举类实现接口的情况
*
* Author: cui
* DATE: 2022/4/2 22:42
*/
public class SeasonTest02 {
public static void main(String[] args) {
//2、values()
System.out.println("*************values()**************");
Season2[] values = Season2.values();
for (int i = 0; i < values.length; i++) {
System.out.println(values[i]);
values[i].show();
}
}
}
//接口
interface info{
void show();
}
//使用enum关键字定义枚举类
enum Season2 implements info{
//1、提供当前枚举类的对象，多个对象之间用逗号隔开，末尾的对象分号结束
SPRING("春天","吹暖花开"){
@Override
public void show() {
System.out.println("这是春季");
}
},
SUMMER("夏天","夏日炎炎"){
@Override
public void show() {
System.out.println("这是夏季");
}
},
AUTUMN("秋天","秋高气爽"){
@Override
public void show() {
System.out.println("这是秋季");
}
},
WINTER("冬天","冰天雪地"){
@Override
public void show() {
System.out.println("这是冬季");
}
};
//2、声明Season对象的属性
private final String seasonName;
private final String seasonDesc;
//3、私有化类的构造器,并给对象属性赋值
private Season2(String seasonName,String seasonDesc){
this.seasonName = seasonName;
this.seasonDesc = seasonDesc;
}
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
// @Override
// public void show() {
// System.out.println("这是一个季节");
// }
}
