Question

I am using Scanner for taking user input in java. when i use nextInt() and the user inputs “2 5”, then the value “2” is assigned and 5 is thrown away. What if I want to display that such an input is an error?
One solution that comes to my mind is that i can use nextString() instead of nextInt() and then work my way out. But can anybody suggest a better solution?

i realized that it is not throwing away the integer after space, instead it is using it for the next input.

import java.util.Scanner;
class Test{
static Scanner in=new Scanner(System.in);
static void trial(){
    int k=in.nextInt();
    System.out.println(k);
    System.out.println(k);
}

public static void main(String[] args){     
    int k=in.nextInt();
    System.out.println(k);
    System.out.println(k);
    trial();        
}
}

Answer 1

1. First use nextLine() to read the entire line.

2. Use Integer.parseInt() method to validate the integer input.

Eg:

Scanner scan = new Scanner(System.in);
String s = scan.nextLine();

try{
    Integer.parseInt(s);
}
catch(NumberFormatException ex){
    System.out.println("Its not a valid Integer");
}