Getting java.lang.NumberFormatException in the code

Question

Code :

I have TriangleSummer class which has class variable

static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

My main function is

public static void main(String args[]) throws IOException {
    int noOfTestCases = Integer.parseInt(reader.readLine());
    for(int i=0;i<noOfTestCases;i++){
        int noOfEntries = Integer.parseInt(reader.readLine());
        System.out.println(computeMaxSum(noOfEntries));
    }
}

Relevant part of my computeMaxSum() method is

public static int computeMaxSum(int noOfEntries) throws IOException {

    int[][] triangle = new int[noOfEntries][noOfEntries];

    for(int j=0;j<noOfEntries;j++){
        int k=0;
        for(String str : reader.readLine().split(" ")){
            triangle[j][k] = Integer.parseInt(str);
            k++;
        }
    }
  //further logic nothing to do with I/O
 }

and finally stack trace is

Exception in thread "main" java.lang.NumberFormatException: For input string: "4 "
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:492)
    at java.lang.Integer.parseInt(Integer.java:527)
    at Matrices.TriangleSummer.main(TriangleSummer.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

for the input

2
3
1
2 1
1 2 3
4 
1 
1 2 
4 1 2
2 3 1 1 

So I am getting NumberFormatException while reading line number 6 i.e value 4 at line

int noOfEntries = Integer.parseInt(reader.readLine());

. And I am completely clueless so as to why?

Answer 1

 java.lang.NumberFormatException: For input string: "4 "

It seems there is space at end. Do a trim() before passing to Integer.parseInt(str);

Answer 2

Remove the space from string "4 ", using String#trim()

It returns a copy of the string, with leading and trailing whitespace omitted

Code snippet -

for(String str : reader.readLine().split(" ")){
     triangle[j][k] = Integer.parseInt(str.trim());
     k++;
}

Answer 3

this one will remove your spaces

int n=Integer.parseInt(br.readLine().trim());