枚举&注解
作者：互联网
一、枚举&注解
如何自定义枚举类
public class TestSeason {
Season spring = Season.SPRING;
}
class Season {
// 1.提供类的属性，声明为private final
private final String seasonName;
private final String seasonDesc;
// 2.声明final的属性，在构造器中初始化
private Season(String seasonName,String seasonDesc) {
this.seasonName = seasonName;
this.seasonDesc = seasonDesc;
}
// 3.通过公共的方法来调用属性
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
// 4.创建枚举类的对象:将类的对象声明为public static final
public static final Season SPRING = new Season("spring", "春暖花开");
public static final Season SUMMER = new Season("summer", "夏日炎炎");
public static final Season AUTUMN = new Season("autumn", "秋高气爽");
public static final Season WINTER = new Season("winter", "白雪皑皑");
@Override
public String toString() {
return "Season [seasonName=" + seasonName + ", seasonDesc=" + seasonDesc + "]";
}
}
如何使用enum关键字定义枚举类
1.常用的方法
public class TestSeason {
Season spring = Season.SPRING;
//1.valus()方法
Season[] seasons = Season.values();
//2.valueOf(String name):要求传入的形参name是枚举类对象的名字
//否则，报java.lang.IllegalArgumentException异常
String str = "SPRING";
Season season = Season.valueOf(str);
Thread.State[] states = Thread.State.values();
}
enum Season {
SPRING("spring", "春暖花开"),
SUMMER("summer", "夏日炎炎"),
AUTUMN("autumn", "秋高气爽"),
WINTER("winter","白雪皑皑");
private final String seasonName;
private final String seasonDesc;
private Season(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 + "]";
}
}
2.如何让枚举类实现接口：可以让不同的枚举类的对象调用被重写的抽象方法，执行的效果不同。（相当于让每个对象重写抽象方法）
interface Infomation{
public abstract void show();
}
enum Season implements Infomation{
SPRING("spring","春暖花开"){
public void show(){
System.out.println("春天");
}
},
SUMMER("summer","夏日炎炎"){
public void show(){
System.out.println("夏天");
}
},
AUTUMN("autumn","秋高气爽"){
public void show(){
System.out.println("秋天");
}
},
WINTER("winter","白雪皑皑"){
public void show(){
System.out.println("冬天");
}
};
private final String seasonName;
private final String seasonDesc;
private Season(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 + "]";
}
}
注解Annotation
1.注解（Annotation）概述
从JDK5.0开始，Java增加了对元数据（MetaData）的支持，也就是Annotation（注解）
Annotation其实就是代码里的特殊标记，这些标记可以在编译，类加载，运行时被读取，并执行相应的处理。通过使用Annotation，程序员可以在不改变原有逻辑的情况下，在源文件中嵌入一些补充信息。
Annotation可以像修饰符一样被使用，可用于修饰包，类，构造器，方法，成员变量，参数，局部变量的声明，这些信息被保存在Annotation的“name=value”对中
Annotation能被用来为程序元素（类，方法，成员变量等）设置元数据
2.使用Annotation时要在其前面增加@符号，并把该Annotation当成一个修饰符使用。用于修饰它支持的程序元素。三个基本的Annotation
@Override：限定重写父类方法，该注释只能用于方法
@Deprecated：用于表示某个程序元素（类，方法等）已过时
@SuppressWarnings：抑制编译器警告。
3.如何自定义一个注解
public @interface MyAnnotation {
String value() default "hello";
}
4.元注解。JDK的元Annotation用于修饰其他Annotation的定义。JDK5.0提供了专门在主街上的注解类型，分别是
Retention
Target
Documented
Inherited
标签：String,Season,枚举,Annotation,seasonName,seasonDesc,注解,public 来源： https://blog.csdn.net/weixin_44145972/article/details/88926536