Different Approaches for Reversing a String in Java

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When you are applying for a job that requires technical programming skills in a coding language such as Java, you may be given a test.

For example, you may be asked how to reverse a string in Java. But what if you don?t know how to solve this problem?

How will you respond to this coding challenge?

Some Potential Job Application Scenarios

If you are new to getting a job in Java programming, you may be wondering what the process is to get hired. Well, this will depend entirely on the company you are applying for. Some companies will look at your resume, talk to your references, have a brief interview, and hire you. Others may want to see examples of work you have done.

Here are some things you should be prepare for:

1. Java Programming Tests

When you are applying for a job as a Java programmer, you may be given some programming tests. If you are lucky, some of these will be provided online and you can do them ?open book.? This means, you could go and search online to get help with your programming solution.

This would not really be cheating, as typically, a good programmer these days will always go online and check message boards and places like Stack Overflow to ask questions and get help with coding conundrums.

Some of these tests may be timed, so be prepared ahead of time and bone up on your Java before taking your coding test.

2. Interviewer Questions

Your interviewer may also ask you how to code something during an interview. No, you cannot be expected to rattle off a bunch of code from memory on the spot. However, be prepared to give some potential avenues for solving the coding problem.

For example, if the interviewer asks you how you might use Java to create a specific type of web-based application, you could give them your recommended approach to solving the problem.

Being specific here is good, but not so specific you make your interviewer?s eyes glaze over.

Here Is Our Example Coding Test and Interview Question

Okay, so let us pretend you are applying for a job and are given the following either in a test format or the interviewer asks:

Can you reverse a string in Java?

They may even give you an example string. Let us take the standard ?Hello World? as our string of choice.

Before you get started, you should ask any questions you need for clarification, such as:

  • What type of output are you looking for?
  • Do you want it printed to the screen or to a file?
  • Etc.

This brings us to our next issue, which is important for clarification, what exactly does it mean to reverse a string in Java?

What Exactly Does It Mean to Reverse a String in Java?

Before you go off and start doing your Java coding, make sure you get some clarification on what exactly they want. And be clear on what you are doing.

In this case, we are talking about a ?string? that needs to be reversed.

By this point, if you are applying for a job in Java, we hope that you already know that we are not talking ?string? as in a really skinny piece of rope. We are talking about a string of characters, in this case: ?Hello World!?

This is where even a simple-sounding instruction really need clarification. Are you reversing the order of the words, or are you reversing all the characters?

If you are reversing the words, then ?Hello World!? becomes ?World! Hello? ? and we can further nitpick and create some code to leave the punctuation in place, so the reverse output would be ?World Hello!?

If you are reversing the characters, then ?Hello World!? becomes ?!dlroW olleH? ? which is an entirely different result and requires very different code.

Here?s another potential reversal, changing ?Hello World? by reversing the individual words (we?ll leave the exclamation point in place), which gives you: “olleH dlroW!”

Get some clarity on this before submitting your answer to your interviewer.

Different Ways to Reverse a String in Java

You would think such a simple problem as reversing a string of characters would have an easy solution. Well, it does, but then you can get into long, protracted discussions about how to do this on Stack Overflow.

Still, going to Stack Overflow should be your first line of attack in trying to solve any coding problem. As you can see from this discussion here about string reversal, you will learn a lot about how to approach the problem.

Here are some other ways to handle a string reversal in Java code:

1. The Simple Way in to Reverse a String in Java

The simplest way to reverse all the characters in a string is to use the StringBuilder function:

new StringBuilder(“hi”).reverse().toString()

This turns ?Hello World!? into ?!dlroW olleH? ? yay!

However, this solution is not recommended for multi-threaded applications, but do you really need to worry about that in some sample test code?

You can also find many other example methods here.

2. How to Swap the Order of Words Using Java

Here is some sample code from this Java tutorial website on how to swap out one word for another.

public class StringReverse {

???public static void main(String[] args) {

???????String str = “Hello World!”;



???private static String reverse(String originalString) {

???????StringBuilder result = new StringBuilder();

???????String[] words = originalString.split(“\\s+”);

???????for (int i = words.length – 1; i >= 0; i–) {

???????????result.append(words[i]).append(‘ ‘);


???????return result.toString().trim();



This means ?Hello World!? becomes ?World! Hello? when done.

3. How to Reverse Characters Within Individual Words

Here, also at Stack Overflow, you can find examples of numerous ways to reverse characters within words using Java. There, you can find 30 answers exploring different ways of solving the problem and exploring the merits and demerits of each. The number one answer is:

String source = “Hello World!”;

for (String part : source.split(” “)) {

???System.out.print(new StringBuilder(part).reverse().toString());

???System.out.print(” “);


When this is finished, our ?Hello World? becomes “olleH dlroW!” ? nifty!


Ethics of Using Other People?s Code for Programming Tests

There is one final thing we need to look at before sending you off to your job interview or coding test. You need to be careful about the code you use when being tested. You do not want to steal a huge bunch of code from someone and pass it off as your own.

Where is the line, however? As you can see from our first example, the very simple basics of reversing a string in Java is not something you can rewrite. You can?t be creative with programming code the same way you can when writing an article or painting a painting.

Sometimes, a solution is just the solution. It is the only way to solve the problem and that is what you need to submit.

However, as a program gets more complicated, the choices you make become more nuanced. You need to use different ways to get at a problem and also write your code out in a way that marks it as your own.

While there is no easy answer to this question as to where the line is, the short answer is that the longer the code, the more likely it is that you can be found ?stealing.?

However, as one person suggests on Stack Overflow, make sure you can explain how your code works, because that will often make the difference on a test.

If you have any questions or concerns about this, you might ask your interviewer or tester what their policies are. Of course, you don?t want to give them an idea that you might just plagiarize code here and there.

You could explain to them that the answer is a stock answer that is standard for how other programmers might approach the problem.

Knowing Code Tricks for Job Interviews

If you know some code tricks, such as how to reverse a string in Java, you may have a leg up in job interviews and screenings. While some of this information may not be easy to memorize, knowing how to find solutions and troubleshoot is still a great quality in an employee. Remember to accentuate the positive when applying for your next tech job.


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