Input problems

Question

hi,
i wrote my firs code in java which needs an integer input. I tried readLine & readInt methods. But the compiler is showing an unidentified IOException error. It says tht exception shd be caught or thrown. My input statement is not workin if i do so...can neone hlp me out..
import java.io.*;
import java.lang.*;
class IntegerPalin
     int palinCheck(int k)
          int n=k;
          int p=0;
          while(k>0)
               p=p+(k%10);
               p=p*10;
               k=k/10;
          if (p==n)return(1);
          else return (0);
class IntPalin     
     public static void main(String args[])
          int m;
     InputStreamReader in = new InputStreamReader(System.in);
     BufferedReader in1 = new BufferedReader(in);
     System.out.println("enter an integer");
m = Integer.ParseInt(in1.readLine());
     IntegerPalin  I = new IntegerPalin();
          int l = I.palinCheck(m);
     if(l==l)
     System.out.println("its a palindrome");
     else
     System.out.println("its not a palin");
}          if I do try -catch iam not getting any error but input is not successful

Answer 1

First of all you appear to have a logic error (i didn't more carefully analyze your code)
if(l==l)
     System.out.println("its a palindrome");
else
     System.out.println("its not a palin");l will always == l even when it's 0 and therefore always evaluate to true even if l is not a palindrome. My best advice is to change the return type of palinCheck(int) to boolean from integer. Then simply change the code to be
if (I.palinCheck(m)){
Now as for your other problem:
This code (at least when I compiled it =) should get an integer from System.in
import java.io.*;
public class GetIntegerFromSystemInput{
    public static void main(String[] args){
        int m = 0;
        System.out.println("Enter an integer: ");
        try{
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            m=Integer.parseInt(br.readLine());
        } catch (Exception e){
            e.printStackTrace();
            System.exit(1);
        System.out.println("The integer you entered is: "+m);
}parseInt(String) only takes a String entirely made out of numbers. For instance 13421 . If the string is 13,142 (you added a comma for example) then it will throw a NumberFormatException instead of a number so no commas or other formatting or characters are allowed.
Just a few code style tips (as having taken CS class before). If you are wondering if something is a palindrome generally name your function isPalindrome with a boolean return type. This make it less likely to run into logic errors like the one you hit.
Now the code will look something like this:
if (isPalindrome(m)){
//true condition
else
//false condition
Then you can read it as (if m is a palindrome do this else do that).
Also this is a perfect case for a static method. You shouldn't have to instantiate a class just to get a method that requires nothing of an instance variable.
static boolean isPalindrome(int k){
if (condition)
return true;
else
return false;
}now you can clean that code up to just have to say:
if (IntegerPalin.isPalindrome(m)){
//true code
else
//false codeand erase all that
IntegerPalin I = new IntegerPalin();
int l =I.palinCheck(m) stuffhope this helps