Java Number Format Exception

Question

I was solving aquestion on CodeChef platform when I faced a NumberFormatException.

First I used Scanner for handling the inputs, then BufferedReader. But none of them worked!

Here is my code:

import java.io.*; import java.util.*; import java.text.*; import java.math.*; import java.util.regex.*; class Practise { public static void main(String[] args) throws IOException{ BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); int t = Integer.parseInt(br.readLine()); while(t > 0) { String s = br.readLine(); ArrayList<String> al = new ArrayList<>(); int i = 0; while(i < s.length()) { String temp = ""; while(s.charAt(i) != ' '){ temp += s.charAt(i); i++; if(i >= s.length()) { break; } } al.add(temp); i++; } if(al.contains("not")) { System.out.println("Real Fancy"); } else { System.out.println("regularly Fancy"); } t--; } } }

What could the problem be?

Input -->The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows. -->The first and only line of each test case contains a single string S denoting a quote.

The Exception message i am getting-

Exception in thread "main" java.lang.NumberFormatException: null at java.lang.Integer.parseInt(Integer.java:542) at java.lang.Integer.parseInt(Integer.java:615) at Practise.main(Main.java:11)

int t=Integer.parseInt(br.readLine()); make sure the value of br.readLine() is pure number — flyingfox
– flyingfox, Commented Jan 5, 2019 at 13:17
t is an integer from 1 to 50 and it is passing all the custom test cases — Nishi
– Nishi, Commented Jan 5, 2019 at 13:33
use debugger, stop just before the line which exception is thrown and see the br.readLine() value, then probably you'll see that is not a just a number. — Amir Hedieh
– Amir Hedieh, Commented Jan 5, 2019 at 13:34

CodeMatrix · Accepted Answer · 2019-01-05 13:23:47Z

Documentation:

* Thrown to indicate that the application has attempted to convert * a string to one of the numeric types, but that the string does not * have the appropriate format.

The exception will be thrown at the line int t = Integer.parseInt(br.readLine());. The reason why the exception will be thrown there is that the input that you read there isn't a Number. If it is a number + a String or something else it will throw the NumberFormatException.

Example input 1235a

This will throw an exception with the following message:

java.lang.NumberFormatException: For input string: "1235a"

So you should debug what the input there is.

Input: The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows. The first and only line of each test case contains a single string S denoting a quote.
From the exception you get the message that your input is null that means that there is no input was given. That causes your exception.

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