Reverse a String and store it in the same variable in Java using String class methods

Question

Suppose there is a string variable str = "A man is no one!", then i need the reverse of this string to be stored in same str variable as "!eno on si nam A", without using any other object or variable. Could someone please provide the most optimized way to do this?

I already used below piece of code:

public static String reverseRecursively(String str) {
        //base case to handle one char string and empty string
        if (str.length() < 2) {
            return str;
        }
        return reverseRecursively(str.substring(1)) + str.charAt(0);
    }

Any other way of doing this?

Please note that I only want it using String class methods.

Could you provide your not optimized way? – takendarkk Aug 08 '16 at 17:33 — takendarkk, Aug 08 '16 at 17:33

apetranzilla · Accepted Answer · 2016-08-08T17:47:58.663

2

Try this.

new StringBuilder(str).reverse().toString()

While this does create a new StringBuilder instance, it doesn't store it in a variable, and it would be very tricky (if possible) to reverse the string without ANY new objects whatsoever.

Edit

Since you don't want to use anything but String methods, here's a simple way to do it with a loop instead, but again it still creates new objects.

char[] chars = new char[str.length()];
for (int i = 0; i < str.length(); i++) {
    chars[str.length() - i - 1] = str.charAt(i);
}
String newStr = new String(chars);

edited Aug 08 '16 at 17:47

answered Aug 08 '16 at 17:25

apetranzilla

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I do not want to use StringBuilder. I want to reverse using only String class methods. – Shashank Shekher Aug 08 '16 at 17:41
@ShashankShekher I've updated my answer. – apetranzilla Aug 08 '16 at 17:48
Any other solution? – Shashank Shekher Aug 08 '16 at 17:53
@ShashankShekher What's wrong with the one I just made? What are the requirements? – apetranzilla Aug 08 '16 at 17:56
Nothing wrong. Just want to know if there's any other approach. – Shashank Shekher Aug 09 '16 at 16:40
@ShashankShekher there's definitely other approaches but these are the simplest. – apetranzilla Aug 09 '16 at 16:48
Okay. Thanks for the solution! – Shashank Shekher Aug 09 '16 at 16:59

Reverse a String and store it in the same variable in Java using String class methods

1 Answers1