Reverse string code error

Question

The program supposed to ask the user to enter a string then the program will reverse it and display it, but the code only return the first letter

import java.util.*;

public class ReverseString {

    public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    System.out.print("Enter a String: ");
    String s = scan.next();

        int x = s.length();

        char c = ' ';
        for(int i=x-1; i>=0;i--){
                c = s.charAt(i);
        }

            System.out.print("The reverse of String " + s + " is ");
            System.out.print(c);

    }
}

Output:

    Enter a String: Welcome
    The reverse of String Welcome is W

You don't ever create a new string (just a single character assignation from last character to first character) — KevinDTimm, Dec 20 '13 at 14:15
I wasn't going to use char but the teacher used it in an example different from this and then asked to solve this I was wondering how would it work. Thanks for the help all :D ! — Deem, Dec 20 '13 at 21:12

Prabhakaran Ramaswamy · Answer 1 · 2013-12-20T14:22:05.760

1

Change char c = ' '; to String reverse=""; and append the character to it for each iteration.

The problem in your code is char c can hold only one character at a time.

Do like this

 String reverse ="";
 for(int i=s.length()-1; i>=0;i--){
      reverse += s.charAt(i);
 }

 System.out.print(reverse);

edited Dec 20 '13 at 14:22

answered Dec 20 '13 at 14:15

Prabhakaran Ramaswamy

25,706
10
57
64

**Please don't teach string concatenation like this**. They might continue to use it. Use `StringBuilder`. – tilpner Dec 20 '13 at 16:29

score 1 · Answer 2 · answered Dec 20 '13 at 14:15

1

You're overwriting value of c in each iteration, change it to string and add to it in the loop

String c = "";
for(int i=x-1; i>=0;i--){
  c += s.charAt(i);
}

answered Dec 20 '13 at 14:15

Konstantin

3,254
15
20

**Please don't teach string concatenation like this**. They might continue to use it. Use `StringBuilder`. – tilpner Dec 20 '13 at 16:30

score 1 · Answer 3 · answered Dec 20 '13 at 14:40

A character is one letter; not a string.... the easiest way to do this, would be to use a StringBuilder like so -

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    System.out.print("Enter a String: ");
    String s = scan.next();

    // int x = s.length();
    // char c = ' ';
    // for (int i = x - 1; i >= 0; i--) {
    //  c = s.charAt(i);
    //}
    StringBuilder c = new StringBuilder(s);
    c = c.reverse();
    System.out.print("The reverse of String " + s + " is ");
    System.out.print(c);
}

Or, if you want to use your current approach you can (by printing one character at time) like this -

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    System.out.print("Enter a String: ");
    String s = scan.next();

    System.out.print("The reverse of String " + s + " is ");
    int x = s.length();
    for (int i = x - 1; i >= 0; i--) {
        char c = s.charAt(i);
        System.out.print(c);
    }
    System.out.println();
}

score 0 · Answer 4 · answered Dec 20 '13 at 14:27

0

If you want to make laugh your teacher (or maybe not) ;)

org.apache.commons.lang.StringUtils.reverse(s)

or without lib:

new StringBuffer(s).reverse().toString();

answered Dec 20 '13 at 14:27

Kloe2378231

1,404
11
12

score 0 · Answer 5 · answered Dec 20 '13 at 15:20

More efficient approach:

char[] strArray = s.toCharArray();

int len = strArray.length;
int max = (int)Math.ceil(len / 2.0);

char t;
for (int i = 0; i < max; ++i) {
  t = strArray[i];
  strArray[i] = strArray[len - i - 1];
  strArray[len - i - 1] = t;
}

System.out.println(String.valueOf(strArray));

Reverse string code error

5 Answers5