java.lang.Enum<E>

• static Enum valueOf(Class enumClass, String name)
  返回指定名字、给定类的枚举常量。
• String toString()
  返回枚举常量名。
• int ordinal()
  返回枚举常量在enum声明中的位置，位置从0开始计数。
• int compareTo(E other)
  如果枚举常量出现在other之前，则返回一个负值；如果this==other，则返回0；否则返回正值。枚举常量的出现次序在enum声明中给出。

package enums;

import java.util.*;
/**
 * This program demonstrates enumerated types
 * @author Mr.Ding
 *
 */

public class EnumTest {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        System.out.println("Enter a size:(SMALL, MEDIUM, LARGE, EXTRA_LARGE)");
        String input = in.next().toUpperCase();
        Size size = Enum.valueOf(Size.class, input);
        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 _.");
        }
    }
}


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