package com.study.study13enum_;
public class Enumeration01 {
public static void main(String[] args) {
//使用
Season spring = new Season("春天", "温暖");
Season summer = new Season("夏天","炎热");
Season autumn = new Season("秋天","凉爽");
Season winter = new Season("冬天","寒冷");
//因为对于季节而言,她的对象是具体的 固定的 不会有更多
//不能体现季节是固定的 引出枚举类
}
}
class Season{
private String name;
private String desc;//描述
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;
}
}
package com.study.study13enum_;
public class Enumeration02 {
public static void main(String[] args) {
System.out.println(Season1.AUTUMN);
System.out.println(Season1.SPRING);
}
}
//演示定义枚举实现
class Season1 {
private String name;
private String desc;//描述
//1.将构造器私有化 目的 防止直接new
//2.去掉set方法 防止属性被修改
//3.在Season内部,直接创建固定的属性
//4.可以加入final 修饰符
public static final Season1 SPRING =new Season1("春天", "温暖");
public static final Season1 SUMMER =new Season1("夏天", "炎热");
public static final Season1 AUTUMN =new Season1("秋天", "凉爽");
public static final Season1 WINTER =new Season1("冬天", "寒冷");
private Season1(String name, String desc) {
this.name = name;
this.desc = desc;
}
@Override
public String toString() {
return "Season1{" +
"name='" + name + '\'' +
", desc='" + desc + '\'' +
'}';
}
public String getName() {
return name;
}
public String getDesc() {
return desc;
}
}
package com.study.study13enum_;
public class Enumeration03 {
public static void main(String[] args) {
System.out.println(Season2.SPRING);
System.out.println(Season2.AUTUMN);
System.out.println(Season2.SUMMER);
System.out.println(Season2.WINTER);
}
}
enum Season2{
//1.使用枚举类 用enum来代替 class
//2.SPRING("春天", "温暖"); 常量名(实参列表)
//3.如果有多个常量(对象),是用逗号间隔 即可
//4.如果使用enum来实现枚举,要求将定义对象,写在前面
//5.如果使用无参构造器,创建常量对象,则可以省略()
WINTER("冬天", "寒冷"),
SUMMER("夏天", "炎热"),
SPRING("春天", "温暖"),
WHAT,
AUTUMN("秋天", "凉爽");
private String name;
private String desc;//描述
//
private Season2() {
}
private Season2(String name, String desc) {
this.name = name;
this.desc = desc;
}
@Override
public String toString() {
return "Season1{" +
"name='" + name + '\'' +
", desc='" + desc + '\'' +
'}';
}
public String getName() {
return name;
}
public String getDesc() {
return desc;
}
}
package com.study.study13enum_;
import com.study.study13enum_.Season2;
public class EnumMethod {
public static void main(String[] args) {
//使用Season2枚举类,来演示各种方法
Season2 autumn=Season2.AUTUMN;
//输出枚举对象的名字
System.out.println(autumn.name());
//ordinal()输出对象的编号 从零开始
//AUTUMN 枚举对象是第五个 所以输出4
System.out.println(autumn.ordinal());
//从反编译可以看出 values方法,返回Season2[]
//含有定义的所有枚举对象
Season2 values[]=Season2.values();
System.out.println("=======遍历取出枚举对象=======");
for(Season2 season:values){//增强for循环
System.out.println(season);
}
//valueOf:将字符串转化成枚举对象,要求字符串必须为已有的常量名,否则报异常
//执行流程
//1.根据你输入的:“AUTUMN”到Season2的枚举对象去查找
//2.如果找到了,就返回,如果没有 就报错
Season2 autumn1=Season2.valueOf("AUTUMN");
System.out.println("autumn1="+autumn1);
System.out.println(autumn==autumn1);
//compareTo:比较两个枚举常量,比较的是编写
//1.就是把Season.AUTUMN 枚举对象的编号和Season.SUMMER 枚举对象的编号进行比较
System.out.println(Season2.AUTUMN.compareTo(Season2.SUMMER));
//
// int nums[]={1,2,9};
// //普通for循环
// System.out.println("=======普通for循环==========");
// for (int i = 0; i < nums.length; i++) {
// System.out.println(nums[i]);
// }
// System.out.println("========增强for循环==========");
// for(int i:nums){//执行流程 依次从nums数组中 取出数据 取出完毕 退出增强for循环
// System.out.println("i="+i);
//
// }
}
}
package com.study.study13enum_;
public class EnumExercise02 {
public static void main(String[] args) {
Week weeks[]=Week.values();
for(Week week:weeks){
System.out.println(week);
}
}
}
enum Week{
Monday("星期一"),
Tuesday("星期二"),
WEDNESDAY("星期三"),
THURSDAY("星期四"),
FRIDAY("星期五"),
SATURDAY("星期六"),
SUNDAY("星期天");
private String name;
private Week(String name) {
this.name = name;
}
@Override
public String toString() {
return name;
}
}
package com.study.study13enum_;
public class EnumDetail {
public static void main(String[] args) {
Season3.ClassicMusic.play();
}
}
enum Season3 implements IPlaying{
ClassicMusic;
@Override
public void play() {
System.out.println("播放好听的音乐");
}
}
interface IPlaying{
public void play();
}
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 .
package com.study.study14annotation_;
public class Override_ {
public static void main(String[] args) {
}
}
class Father{
public void fly(){
System.out.println("Father...");
}
}
class Son extends Father{
@Override
//1. @Override注解放在fly方法上,表示子类重写了父类的fly()方法
//2.如果没有写@Override注解,还是会重写
//3.如果写了Override 注解,编译器就回去检查方法是否真的重写了父类的方法
//如果的确重写 编译通过 如果没有构成重写 则编译错误
//4.Override的定义
//如果发现 @interface 表示一个注解类
/*
* @Target(ElementType.METHOD) //@Target修饰注解的注解 称为源注解
* @Retention(RetentionPolicy.SOURCE)
* public @interface Override {
* }
*/
public void fly() {
System.out.println("Son...");
}
}
package com.study.study14annotation_;
public class Deprecated_ {
public static void main(String[] args) {
A a = new A();
a.hi();
System.out.println(a.n1);
}
}
//1.Deprecated 修饰某个元素,表示该元素已经过时
//2.即不再推荐使用,但是仍然可以使用
//3.查看 @Deprecated 注解类的源码
//4.可以修饰方法,类,字段,包,参数 等等
//5.@Deprecated可以做版本升级 过渡使用
/*
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(value={CONSTRUCTOR, FIELD, LOCAL_VARIABLE, METHOD, PACKAGE, PARAMETER, TYPE})
public @interface Deprecated {
}
*/
@Deprecated
class A{
@Deprecated
public int n1=10;
@Deprecated
public void hi(){
}
}
package com.study.study14annotation_;
import java.util.ArrayList;
import java.util.List;
@SuppressWarnings({"all"})
public class SuppressWarnings_ {
//1.当我们不希望看到这些警告的时候,可以使用SuppressWarnings注解来抑制警告信息
//2.在{""}中,可以写入你希望抑制(不显示)警告信息
//3.all
//4关于SuppressWarnings作用范围是和你放置的位置相关
// 比如@SuppressWarnings放置在main 方法,那么抑制警告的范围就是 main
//通常我们可以放置具体的语句,方法,类
//5.源码
/* @Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})//放置的位置
@Retention(RetentionPolicy.SOURCE)
public @interface SuppressWarnings {
String[] value(); //该注解类有数组
}*/
@SuppressWarnings({"all"})
public static void main(String[] args) {
List list=new ArrayList();
list.add("");
list.add("");
list.add("");
int i;
System.out.println(list.get(1));
}
}
JDK 的元 Annotation 用于修饰其他 Annotation