Shifting characters within a string

Question

String newStr;

public RandomCuriosity(String input){
    newStr = input;
}

public void shiftChars(){
    char[] oldChar = newStr.toCharArray();
    char[] newChar = new char[oldChar.length];
    newChar[0] = oldChar[oldChar.length-1];
    for(int i = 1; i < oldChar.length; i++){
        newChar[i] = oldChar[i-1];
    }
    newStr = String.valueOf(newChar);
}

I created a method that shifts characters forward by one. For example, the input could be:

The input: Stackoverflow

The output: wStackoverflo

How I did it is I mutated an instance of a string. Convert that string to a char array (calling it oldChar), assigned the last index of of oldChar as the first index of newChar, and made a for-loop that took the first index of oldChar as the second index of my new Char array and so forth. Lastly, I converted the char array back to a string.

I feel like I did way too much to do something very simple. Is there a more efficient way to do something like this?

EDIT Thanks for the great answers!

Solution 1

newStr = newStr.charAt(newStr.length() - 1) + newStr.substring(0, newStr.length() - 1);

Solution 2

You can made your life simpler :

public static void main (String[] args) throws java.lang.Exception {
    String input = "Stackoverflow";
    for(int i = 0; i < s.length(); i++){
        input = shift(input);
        System.out.println(input);
    }
}

public static String shift(String s) {
    return s.charAt(s.length()-1)+s.substring(0, s.length()-1);
}

Output :

wStackoverflo
owStackoverfl
lowStackoverf
flowStackover
rflowStackove
erflowStackov
verflowStacko
overflowStack
koverflowStac
ckoverflowSta
ackoverflowSt
tackoverflowS
Stackoverflow

Comments

[theGreenCabbage]

Woah. That's an intense one-liner. So let me get this straight. You treated the last index as a char, and the chars before the last index as a complete string?

[JB Nizet]

Yes. But you may also use newStr.substring(newStr.length() - 1) as the first operand if you find it clearer.

[theGreenCabbage]

This is a very beautiful solution, and a great use of in-built Java methods. Thanks JB.

[Sotirios Delimanolis]

@JB Can you check my last comment to the question and comment on if I am right about the complexity?

[JB Nizet]

@SotiriosDelimanolis: looks right to me. O(3n) is O(n) though. Anyway, unless the string is really huge, the performance of such a simple task should not be something you would try to optimize.

[theGreenCabbage]

@JBNizet Out of curiosity, is there any thing inherently bad about my original code?

[JB Nizet]

@theGreenCabbage: there's nothing inherently bad, but it's longer and harder to understand than the one-liner that uses higher-level methods. The one-liner does exactly what you intend to do: create a string beginning with the last char and ending with the n-1 first chars. Without javadoc, your implementation requires a deeper analysis to understand what it does. Using frequently used library methods like substring also guarantees that the code will be jitted and benefit from any optimization that might be introduced in the JDK.

[Caco]

Just correcting code line. It is missing () in second newStr.length. Would be: newStr = newStr.charAt(newStr.length() - 1) + newStr.substring(0, newStr.length() - 1);

[Scratte]

Your solution is the same as the accepted answer by JB Nizet.

[Omar Abusabha]

not matter a lot. Actually, just I want to share how I used this code with my problem, thank you to get your attention on the code ^_^

[Scratte]

Your Answer may be deleted though. The idea is to post different answers.