背景:类的对象只有有限个,确定的。举例如下:
> 星期: Monday (星期一)、….、 Sunday (星期天)
> 性别: Man (男)、 Woman (女)
> 季节: Spring (春节).…….. Winter (冬天)
> 支付方式: Cash (现金)、 WeChatPay (微信)、 Alipay (支付宝) BankCard (银
行卡)、 CreditCard (信用卡)
> 就职状态: Busy 、 Free 、 Vocation 、 Dimission
> 订单状态: Nonpayment (未付款)、 Paid (已付款)、 Fulfilled (已配货)、
Delivered (已发货)、 Return 退货》 Checked 已确认)
> 线程状态:创建、就绪、运行、阻塞、死立
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:JDK5.0之前,自定义枚举类
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public class SeasonTest {
public static void main(String[] args) {
Season spring = Season.SPRING;
System.out.println(spring);
}
}
class Season {
//1.声明Season对象的属性:private final修饰
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.提供当前枚举类的对各对象:public static final的
public static final Season SPRING = new Season( "春天" , "春暖花开" );
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" );
//4.其他诉求1: 获取枚举类对象的属性
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
//4.其他诉求2:提供toString()
@Override
public String toString() {
return "Season{" +
"seasonName='" + seasonName + '\ '' +
", seasonDesc='" + seasonDesc + '\ '' +
'}' ;
}
}
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方式二:JDK5.0之后,可以使用enum关键字定义枚举类
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public class SeasonTest1 {
public static void main(String[] args) {
Season1 summer = Season1.SUMMER;
System.out.println(summer);
System.out.println(Season1. class .getSuperclass()); //java.lang.Enum
//values():
Season1[] values = Season1.values();
for ( int i = 0 ; i < values.length; i++) {
System.out.println(values[i]);
}
//valueOf(String objName):返回枚举类中对象时objName的对象。
Season1 winter = Season1.valueOf( "WINTER" );
//如果没有objName的枚举类对象,则抛异常:IllegalArgumentException
// Season1 winter = Season1.valueOf("WINTER1");
System.out.println(winter);
// winter.show();
}
//使用enum关键字定义枚举类
enum Season1 {
//1.提供当前枚举类的对象,多个对象之间用","隔开,末尾对象";"结束
SPRING( "春天" , "春暖花开" ),
SUMMER( "夏天" , "夏日炎炎" ),
AUTUMN( "秋天" , "秋高气爽" ),
WINTER( "冬天" , "冰天雪地" );
//1.声明Season对象的属性:private final修饰
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 Season1(String seasonName, String seasonDesc) {
this .seasonName = seasonName;
this .seasonDesc = seasonDesc;
}
//4.其他诉求1: 获取枚举类对象的属性
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
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使用enum关键字定义的枚举类实现接口的情况
情况一:实现接口,在enum类中实现抽象方法
情况二:让枚举类的对象分别实现接口中的抽象方法
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public class SeasonTest1 {
public static void main(String[] args) {
//values():
Season1[] values = Season1.values();
for ( int i = 0 ; i < values.length; i++) {
System.out.println(values[i]);
values[i].show();
}
}
interface Info {
void show();
}
enum Season1 implements Info {
SPRING( "春天" , "春暖花开" ) {
@Override
public void show() {
System.out.println( "春天在哪里" );
}
},
SUMMER( "夏天" , "夏日炎炎" ) {
@Override
public void show() {
System.out.println( "宁夏" );
}
},
AUTUMN( "秋天" , "秋高气爽" ) {
@Override
public void show() {
System.out.println( "秋天不回来" );
}
},
WINTER( "冬天" , "冰天雪地" ) {
@Override
public void show() {
System.out.println( "大约在冬季" );
}
};
private final String seasonName;
private final String seasonDesc;
private Season1(String seasonName, String seasonDesc) {
this .seasonName = seasonName;
this .seasonDesc = seasonDesc;
}
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
}
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原文链接:https://blog.csdn.net/weixin_49329785/article/details/119656504