一、枚举类的基本介绍
1.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、如何自定义枚举类
1.方式一:jdk5.0之前,自定义枚举类
(1)
public class SeasonTest {
public static void main(String[] args){
Season spring=Season.SPRING;
System.out.println(spring);
}
}
//自定义枚举类
class Season{
//1.声明Season对象的属性:private final修饰
private final String name;
private final String seasonDesc;
//2.私有化类的构造器,并给对象属性赋值
private Season(String name,String seasonDesc){
this.name=name;
this.seasonDesc=seasonDesc;
}
//3.提供当前枚举类的多个对象:public static final
public static final Season SPRING=new Season("春天","春暖花开");
public static final Season SUMMER=new Season("夏天","夏日绵绵");
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.其它诉求1:获取枚举类对象的属性
public String getName() {
return name;
}
public String getSeasonDesc() {
return seasonDesc;
}
//4其它诉求2:提供toString()
@Override
public String toString() {
return "Season{" +
"name='" + name + '\'' +
", seasonDesc='" + seasonDesc + '\'' +
'}';
}
}
三.方式二:jdk5.0,可以使用enum关键字定义枚举类
public class SeasonTest {
public static void main(String[] args){
Season spring=Season.SPRING;
System.out.println(spring);
System.out.println(Season.class.getSuperclass());//说明定义的枚举类继承于class java.lang.Enum
}
}
//使用enum关键字定义枚举类
enum Season{
//1.提供当前枚举类的多个对象,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","夏日绵绵"),
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 name;
private final String seasonDesc;
//2.私有化类的构造器,并给对象属性赋值
private Season(String name,String seasonDesc){
this.name=name;
this.seasonDesc=seasonDesc;
}
//4.其它诉求1:获取枚举类对象的属性
public String getName() {
return name;
}
public String getSeasonDesc() {
return seasonDesc;
}
//4其它诉求2:提供toString()
// @Override
// public String toString() {
// return "Season{" +
// "name='" + name + '\'' +
// ", seasonDesc='" + seasonDesc + '\'' +
// '}';
// }
}
四、Enum类的主要方法
public class SeasonTest {
public static void main(String[] args){
Season spring=Season.SPRING;
//toString()
System.out.println(spring.toString());
// System.out.println(Season.class.getSuperclass());//说明定义的枚举类继承于class java.lang.Enum
//values()
Season[] values=Season.values();
for (int i=0;i<values.length;i++){
System.out.println(values[i]);
}
// Thread.State[] values1=Thread.State.values();
// for (int i=0;i<values1.length;i++){
// System.out.println(values1);
// }
//valueOf(String objName):返回枚举类中对象名是objName的对象
//如果没有objName的枚举类对象,则抛异常
Season winter=Season.valueOf("WINTER");
System.out.println(winter);
}
}
//使用enum关键字定义枚举类
enum Season{
//1.提供当前枚举类的多个对象,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","夏日绵绵"),
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 name;
private final String seasonDesc;
//2.私有化类的构造器,并给对象属性赋值
private Season(String name,String seasonDesc){
this.name=name;
this.seasonDesc=seasonDesc;
}
//4.其它诉求1:获取枚举类对象的属性
public String getName() {
return name;
}
public String getSeasonDesc() {
return seasonDesc;
}
//4其它诉求2:提供toString()
// @Override
// public String toString() {
// return "Season{" +
// "name='" + name + '\'' +
// ", seasonDesc='" + seasonDesc + '\'' +
// '}';
// }
}
五、使用enum关键字定义的枚举类实现接口
1.情况一:实现接口,在enum类中实现抽象方法
public class SeasonTest {
public static void main(String[] args){
Season spring=Season.SPRING;
spring.show();
}
}
interface Info{
void show();
}
//使用enum关键字定义枚举类
enum Season implements Info {
//1.提供当前枚举类的多个对象,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","夏日绵绵"),
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 name;
private final String seasonDesc;
//2.私有化类的构造器,并给对象属性赋值
private Season(String name,String seasonDesc){
this.name=name;
this.seasonDesc=seasonDesc;
}
//4.其它诉求1:获取枚举类对象的属性
public String getName() {
return name;
}
public String getSeasonDesc() {
return seasonDesc;
}
@Override
public void show() {
System.out.println("这是一个季节");
}
}
2.情况二:让枚举类的对象分别实现接口中的抽象方法。
public class SeasonTest {
public static void main(String[] args){
Season spring=Season.SPRING;
spring.show();
}
interface Info{
void show();
}
//使用enum关键字定义枚举类
enum Season implements Info {
//1.提供当前枚举类的多个对象,多个对象之间用","隔开,末尾对象";"结束
SPRING("春天","春暖花开"){
@Override
public void show() {
System.out.println("111");
}
},
SUMMER("夏天","夏日绵绵"){
@Override
public void show() {
System.out.println("222");
}
},
AUTUMN("秋天","秋高气爽"){
@Override
public void show() {
System.out.println("333");
}
},
WINTER("冬天","冰天雪地"){
@Override
public void show() {
System.out.println("444");
}
};
//1.声明Season对象的属性:private final修饰
private final String name;
private final String seasonDesc;
//2.私有化类的构造器,并给对象属性赋值
private Season(String name,String seasonDesc){
this.name=name;
this.seasonDesc=seasonDesc;
}
//4.其它诉求1:获取枚举类对象的属性
public String getName() {
return name;
}
public String getSeasonDesc() {
return seasonDesc;
}
}