Question

This time I have a very lame problem, which was working perfectly but now its not:

        BufferedReader br = new BufferedReader(new InputStreamReader(
                System.in));

        while (br.readLine() != null) {
            System.out.println(br.readLine());
        }

Input file:

1
2
3
4
5
6
7
8
9

In command line: $java myprogram < inputfile

The result of the above written code is:

    2
    4
    6
    8
null

But the expected output should be same as input file!

Where am I going wrong?!

Answer 1

You are calling br.readLine() twice. It’s calling it once in the while condition and once to actually print it out. That’s why you are only printing every other line.

Edit: Your condition should be:

while(br.ready()){
     System.out.println(br.readLine());
}