JAVA中正则匹配灵活运用

package basic.day11;

import java.util.Scanner;
import java.util.Arrays;

public class Demo8 {
  public static void main(String[] args){
    //^\s*[a-dA-D]([,\s]\s*[a-dA-D]){0,3}$
    Scanner in =new Scanner(System.in);
    String answer;
    while(true){
      System.out.println("请输入:");
      answer=in.nextLine();
      if(answer.matches("^\\s*[a-dA-D]([,\\s]\\s*[a-dA-D]){0,3}$")){
        break;
      }else{
      System.out.println("输入有错误，重新输入！"); 
      }
    }
    String[] data=answer.trim().toUpperCase().split("[,\\s]\\s*");
    Arrays.sort(data);
    System.out.println(Arrays.toString(data));
  }
}