Pointing out an interesting quirk with Java's Math.abs() where it actually returns a negative number

ConvertToPositive.java

import java.util.*;

/**
 * Problem statement: Given a number (that is guaranteed to fit within a 32 bit
 * two's compliment integer), print the absolute value of that number.
 *
 * The catch: A two's compliment signed integer has a larger range for negative
 * numbers than it does positive. So simply returning Math.abs() on the input
 * won't always work if the input is Integer.MIN_VALUE (-2147483648).
 */
public class ConvertToPositive {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);

    // This will NOT work if input is Integer.MIN_VALUE (-2147483648)
    // System.out.println(Math.abs(in.nextInt()));

    // Method one: Handle the edge case specifically
    /**/                                      // Add space to comment out
    int input = in.nextInt();
    if (input == Integer.MIN_VALUE) {
      System.out.println("2147483648");
    } else {
      System.out.println(Math.abs(input));
    }
    /**/

    // Method two: just use longs and not ints
    /** /                                    // Delete that space to uncomment
    long input = in.nextLong();
    System.out.println(Math.abs(input));
    /**/

    // Method three: just use strings
    /** /                                    // Delete that space to uncomment
    String input = in.next();
    if (input.charAt(0) == '-') {
      System.out.println(input.substring(1));
    } else {
      System.out.println(input);
    }
    /**/
  }
}

/*
 * The class name of this program is somewhat misleading, since zero is 
 * neither a positive nor negative number, mathematically speaking.
 * However, I didn't feel like naming it "ConvertToNonNegative", even
 * though that is technically more accurate.
 */