Java addition giving wrong answer

Question

I am trying to add four integers ie 4+3+2+1 but i get the value 202

class Task3{
public static void main (String args[]){
    String x=(args[0]);
    int I = Integer.parseInt (x);   
    char c1 = x.charAt(0);
    char c2 = x.charAt(1);
    char c3 = x.charAt(2);
    char c4 = x.charAt(3);
    System.out.println("First and last digit is: " + c1 +"," + c4);
    if (c1 > c4)
        System.out.println("The first digit is larger");
    else
        System.out.println("The second digit is larger");
    int sum = c1 + c2 + c3 + c4;
    System.out.println(sum);
}

}

Answer 1

This is because you are adding numeric values of UNICODE code points, not digits represented by the corresponding characters.

In order to get a digit from a character code, call Character.digit(c1, 10) (ten indicates that you want a decimal digit).

int c1 = Character.digit(x.charAt(0), 10);
int c2 = Character.digit(x.charAt(1), 10);
int c3 = Character.digit(x.charAt(2), 10);
int c4 = Character.digit(x.charAt(3), 10);

Answer 2

replace char c1 = x.charAt(0); with Character.getNumericValue(x.charAt(0))

Answer 3

Change

int sum = c1 + c2 + c3 + c4;

to

int sum = c1 + c2 + c3 + c4 - 4 * '0';

Since c1, c2, c3, c4 are all characters, so a digit say. 4 is taken as '4' that is basically the ASCII value, so to get 4 and not '4' you need to subtract '0' from each of c1, c2, c3, c4, so 4 * '0' subtracted

Answer 4

You are trying to sum up the char s ASCII codes and not the digit values. You have to retrieve the corresponding digit for each character and then evaluate you addition result:

class Task3
{
  public static void main (String args[])
  {
    String x=(args[0]);
    int I = Integer.parseInt (x);   
    char c1 = x.charAt(0);
    char c2 = x.charAt(1);
    char c3 = x.charAt(2);
    char c4 = x.charAt(3);
    int i1 = Character.digit(c1, 10);
    int i2 = Character.digit(c2, 10);
    int i3 = Character.digit(c3, 10);
    int i4 = Character.digit(c4, 10);
    System.out.println("First and last digit is: " + i1 +"," + i4);
    if (i1 > i4)
      System.out.println("The first digit is larger");
    else
      System.out.println("The second digit is larger");
    int sum = i1 + i2 + i3 + i4;
    System.out.println(sum);
  }

}

Answer 5

The reason of the wrong output others already explained it now one of the way to get the correct output

int sum =0;
while(I>0){
    int rem = I%10;
    sum+=rem;
    I = I/10;
}
System.out.println(sum);

Answer 6

I presume you are passing "4321" or similar to the program.

c1 will not be the number 1 but actually the Unicode number representing the character '1' which is actually 31 (in hexadecimal). The latest addition is adding these Unicode numbers.

See http://unicode-table.com/en/ for the list of unicode numbers to characters and also http://docs.oracle.com/javase/tutorial/i18n/text/unicode.html for more details of characters in Java.