Why the following program is printing numbers instead of alphabets

Question

I am trying to print out all the possibilities of a given string for a fixed length 3. Here is my program

import java.util.*;
import java.lang.*;

class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
        String input = "abc";
        int i=0,j=0,k=0;
        for(i=0;i<3;i++){
            for(j=0;j<3;j++){
                for(k=0;k<3;k++){
                   System.out.println(input.charAt(i)+input.charAt(j)+input.charAt(k)); 
                }
            }
        }       
    }
}

But it prints the permutations of numbers in this format. But I intend to print aaa, aab, aac, bbb .. in that fashion.

See: http://stackoverflow.com/questions/8688668/in-java-is-the-result-of-the-addition-of-two-chars-an-int-or-a-char — Tarwirdur Turon, Oct 20 '15 at 10:13
Try concatenating `System.out.println(" "+input.charAt(i)+input.charAt(j)+input.charAt(k));` — Kruti Patel, Oct 20 '15 at 10:14

score 2 · Answer 1 · answered Oct 20 '15 at 10:19

charAt returns an integral type (actually a char which is a 16 bit unsigned integral type in Java). + is simply summing the values.

One way round that is to prefix the expression with an empty string literal: this forces Java to the interpret + as concatenation: "" + input.charAt(/*etc*/

In my opinion this is a flaw in Java permitting + to be used as a string concatenation operator.

score 1 · Accepted Answer · answered Oct 20 '15 at 10:13

1

input.charAt(i) returns a char, which is an integer type. Therefore + performs int addition instead of concatenation of Strings.

Adding an empty String at the start of the expression will solve your problem :

System.out.println(""+input.charAt(i)+input.charAt(j)+input.charAt(k));

answered Oct 20 '15 at 10:13

Eran

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Any idea how to make it generic? In the above code I explicitly wrote 3 loops, but in the run time if I ask the user to give the input string. Let's say he gave string of length 5, I can inject for loops dynamically right. Any solution? – gates Oct 20 '15 at 10:51
@gates You can use a recursive method. – Eran Oct 20 '15 at 10:55
can you provide me some resource in this regard? – gates Oct 20 '15 at 10:56

score 1 · Answer 3 · answered Oct 20 '15 at 10:16

1

You used this line. That can solve your problem.

System.out.println(Character.toString(input.charAt(i))+Character.toString(input.charAt(j))+Character.toString(input.charAt(k)));

char a_char = input.charAt(0); // This is also return only a char

answered Oct 20 '15 at 10:16

Shiladittya Chakraborty

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Why the following program is printing numbers instead of alphabets

3 Answers3