UVA - 465 - Overflow

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;


public class Main {

    public static void main(String[] args) throws IOException {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        StringBuffer sb=new StringBuffer("");
        String m="";
        BigInteger max=new BigInteger(Integer.MAX_VALUE+"");
            while((m=br.readLine())!=null) {
               sb.append(m).append("\n");
               StringBuilder[] str=new StringBuilder[3];
               for(int i=0;i<3;i++){
                   str[i]=new StringBuilder("");
               }
               for(int i=0,counter=0;i<m.length();i++){
                   if(m.charAt(i)>='0' && m.charAt(i)<='9')
                        str[counter].append(m.charAt(i));
                   if(m.charAt(i)=='+' || m.charAt(i)=='*'){
                        counter++;
                        str[counter].append(m.charAt(i));
                        counter++;
                   }
                  
               }
               BigInteger x=new BigInteger(str[0].toString());
               if(x.compareTo(max)==1)
                   sb.append("first number too big\n");
               BigInteger y=new BigInteger(str[2].toString());
               if(y.compareTo(max)==1)
                   sb.append("second number too big\n");
               if("+".equals(str[1].toString())){
                   if(x.add(y).compareTo(max)==1)
                       sb.append("result too big\n");
               }else{
                   if(x.multiply(y).compareTo(max)==1)
                       sb.append("result too big\n");
               }
              
            }
            System.out.print(sb);
    }
}