How To Reverse A String In Java

Java is one of the most well known programming languages in the world, and has been used to create all sorts of popular programs and web pages across the world.

The only problem is, it can be quite difficult to learn, and is fairly advanced. As such, many users find themselves taking many years to fully grasp what it takes. 

You might be having trouble learning Java yourself and find yourself wondering just how to reverse a string in the Java language.

Java does not make it easy for beginners to learn how to reverse a string, but that’s why we are here to help! If you want to learn how to do it yourself, simply read on below, because we are going to take a look at exactly how to do it!

How Do You Reverse A String In Java?

It is important to mention upfront that, within Java, strings are immutable objects, which means that they cannot be changed or modified after they have been created.

Thus, you need to make use of some efficient workarounds in order to reverse a string using Java. 

Each method will also require that you create a new version of each string you plan to reverse, as the existing strings will be immutable.

Let’s take a look at some of the string reversing methods now.

Use StringBuilder

By using this method you can convert a string into a StringBuilder, which basically refers to turning an immutable string into a mutable string.

Once you have created the StringBuilder, you can then use the provided function labeled as “Reverse()”.

Using that function will then reverse everything that is fed into the string, which leads to the final output.

Once the “Reverse()” function has been used, all that then needs to be done is to convert the reversed StringBuilder into a more standard String, by using the function “toString()”.

This function will convert the StringBuilder into a finished immutable string.

Swap Characters

This method makes use of the “toCharArray()” string function which can be used to convert any string into a character array. 

Once you have implemented the “toCharArray()” function, then you will be able to freely manipulate the letters in the string as you see fit.

If you want to reverse them, then you will need to do it manually.

Thus, you would take the first letter, and swap it with the final letter, and so-on and so-forth until the whole string is reversed. 

Thus, this method is generally best if you are simply reversing a single word, as reversing an entire phrase of multiple words would be incredibly time-consuming and even quite difficult. 

Once you have created your new reversed string, you will then want to use the “String.valueOf()” function.

This will convert the character array into a finished and immutable string. 

This method is great if you just need to change a single word, as it is quick and efficient. Just make sure not to use it for strings of many words.

Create A Loop On A New String

To do this method, you will need to start by creating a new string that is similar to the string you want to reverse.

From there, you simply need to iterate the new string, by using the “for loop” function. 

As the iterating process takes place, simply take the letters from the original string and concatenate them.

This involves taking the characters of the original string and adding them to the new string.

This will cause the new string to be formed with all of the characters in reverse order. 

Use A List

To start this method out, begin by converting your string into a character array, by using the “toCharArray()” function.

This will create a list of all of the characters in the string, and then put them into an order. You can then use the array list to quickly and efficiently reverse the letters yourself.

However, if you are using Java Collections Framework, then you can also make use of the efficient built-in function of “reverse()”.

This is a great method to use if you want one that is very efficient and effective.

Stacks

This method will have you creating a stack of the characters in the string, and then using that stack’s “push()” function to gather all of the characters into the stack efficiently.

This is a very useful and ingenious method, as it takes advantage of the fact that stacks make use of a “First In Last Out” order, so as each character is pushed into the stack, they will be pushed in in an order that is reversed! 

Once you have created the stack, you can then easily convert that stack into an immutable string.

Use An XOR Operation

Start out by converting your string into a character array by using the associated function.

Once the character array has been created, all that needs to be done is to use the “(^) operator” function.

This will cause the first and last characters to swap, and then the second and second to last characters, until the whole string is reversed. 

To Conclude

Though Java does not make it overly easy to reverse a string, thanks to Java strings being immutable, it is still possible to reverse them, though it takes a little bit of work.

Each of the methods above works well, but does the job in its own unique way. 

Take a look through the methods we explored above to find the perfect one for your needs!

Frequently Asked Questions

What is charAt in Java?

The charAt function in Java can be used to find specific characters within a string. This helps you to stay on top of your strings and their contents. 

What is Isdigit?

The isdigit function can be used in Java to determine whether or not a character in a string is numerical or not.

What is Java used for?

Java is used to write the code for all applications that make use of the Java engine.

This is why computers once needed to have Java installed in order to function in a satisfactory way.