Java 核心技术（第八版）卷1：基础知识：枚举P182

import java.util.*;
public class EnumTest {
    public static void main(String [] args)
    {
        Scanner in=new Scanner(System.in);
        System.out.print("Enter a size:(SMALL,MEDIUM,LARGE,EXTRA_LARGE)");
        String input=in.next().toUpperCase();
        Size size=Enum.valueOf(Size.class,input);//valueof 是 toString（） 方法的逆方法，即根据字符串返回对应的枚举值,返回枚举的内容,参数为：枚举类，字符串：枚举值
        System.out.println("size="+size);
        System.out.println("abbreviation="+size.getAbbreviation());
        if (size==Size.EXTRA_LARGE)
            System.out.println("Good job -- you paid attention to the _");
        Size [] values_lcg=Size.values();
        System.out.println("I will show you  all the values of enum Size!");
        for (Size s:values_lcg  ) {

            System.out.println(s);

        }

    }

}
enum Size{
    SMALL("S"),MEDIUM("M"),LARGE("l"),EXTRA_LARGE("XL");
    private Size (String abbreviation){this.abbreviation=abbreviation;}
    public  String getAbbreviation(){return abbreviation;}
    private String abbreviation;
}