[java] How to read input with multiple lines in Java

Use BufferedReader, you can make it read from standard input like this:

BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
String line;

while ((line = stdin.readLine()) != null && line.length()!= 0) {
    String[] input = line.split(" ");
    if (input.length == 2) {
        System.out.println(calculateAnswer(input[0], input[1]));
    }
}