Java tips

import java.util.*;
import java.*;
import java.math.*;
public class Main {
    public static  BigInteger xx(BigInteger y) {    
        return y.multiply(BigInteger.valueOf(3));
    } 
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner cin = new Scanner(System.in);
        int t = cin.nextInt();
        int k,top;
        for (int tt=0;tt<t;++tt){
            k = cin.nextInt();
            top = cin.nextInt();
            String s = cin.nextLine();
            char[] ss=s.toCharArray();//string修改单个字符先转成char数组
            ss[0] =  '0';
            s = ss.toString();//再转回去
            BigDecimal x = new BigDecimal(ss);
            //s.charAt(0) = '0';
            //System.out.println(k+" "+ss+" "+top);
            System.out.println(x);
            System.out.println(xx(BigInteger.valueOf(3)));
        }
    }

}