Kotlin vs. Java: What’s the Difference?

While learning Android Development, the debate of Kotlin vs Java often comes up. Both are very popular languages that run on the JVM (Java Virtual Machine). Both these languages are used in web development, desktop applications, server-side development, data processing, and more. In this blog, you will learn about the key differences between Kotlin and Java, their syntax, and understand which one is a better choice for you. So, let’s get started!

Table of Contents

• What is Kotlin?
• What is Java?
• Difference between Kotlin and Java
• Kotlin vs Java: Detailed Comparison
  1. Expressions
  2. Syntax
  3. Code Length
  4. Data Classes
  5. Memory Management
  6. Type Conversion
  7. Smart Cast
  8. Scripting
  9. Null Checks
  10. Jetpack Compose
• Future of Android Development Using Java vs Kotlin
• Conclusion

What is Kotlin?

Kotlin is an open-source programming language that was created by JetBrains in 2010 and made public in 2016. It is a statically typed language, which means that the variable types (like Int, String, etc.) are known during the time of compilation. Kotlin borrows syntax and concepts from other languages like Java, C#, and Scala. This makes it easier for you to understand Kotlin if you have used one of those languages before. So basically, you can think of Kotlin as Java plus a bunch of useful features that make programming easier and safer.

The latest version of Kotlin is 2.2.20, released on September 10, 2025.

What is Java?

Java is a widely used, open-source programming language that was released by Sun Microsystems in 1995. It is also a statically typed language, which means that the variables are checked during the time of compilation. It runs on JVM (Java Virtual Machine), which makes it highly portable across platforms. Over the years, Java has become the backbone of many industries. It is used to power everything from web applications to enterprise systems. The massive community support, strong performance, and cross-platform compatibility of Java have helped it to be one of the most trusted languages for decades.

The latest version of Java is JDK 25, released on September 16, 2025.

Difference between Kotlin and Java

Kotlin vs Java: Detailed Comparison

In this section, we will discuss in detail the comparison of Kotlin and Java by focusing on their major differences to understand their unique strengths. By looking at Kotlin and Java side by side, you will notice what makes each of these two languages special and how they work differently from each other. This will help you make a smart choice while deciding which language to choose for your projects. In this section, we will discuss the differences between Kotlin and Java and also provide insights on which language you should pick for your development journey.

1. Expressions

Java

Unlike Kotlin, Java does not have any string templates or advanced expression support inside strings. In Java, strings are always inside double quotes ” “, and variables or expressions cannot be embedded directly inside them. Instead of that, you need to use concatenation ( + ) or methods like printf and String.format() to get similar results.

Example in Java:

The above Java code is used to define the name and age of a person. It then prints them in a sentence using string concatenation and formatted output.

Output:

Kotlin

In Kotlin, you can use expressions with variables, operators, and method calls. One of the most important features of Kotlin is string templates. This helps you to include variables and expressions directly inside your strings. Kotlin provides you with two types of string templates:

1. Raw String: This string template lets you write strings with multiple lines, including new lines, without the need for any special characters. In Kotlin, raw strings are always written inside triple quotes “””.

Example of Raw String in Kotlin:

Output:

The above Kotlin code is used to create a multi-line raw string using “””. After that, it prints the string exactly the way it is, including the text and line breaks.

2. Escaped String: This is basically a string template where you can use escape sequences (special characters starting with \). Kotlin supports 8 types of escape sequences that are mentioned below:

1. \t → tab
2. \n → new line
3. \\ → backslash
4. \$ → dollar sign
5. \b → backspace
6. \’ → single quote
7. \” → double quote
8. \r → carriage return

Example of Escaped String in Kotlin:

Output:

The above Kotlin code is used to store a string having a new line (\n) escape sequence in a variable. After that, it prints the string on two separate lines.

2. Syntax

Both Java and Kotlin have some differences in their syntax, one of which is the use of semicolons. In Java, you must end every sentence with a semicolon, while in Kotlin, it is not required to use semicolons. Given below is an example that demonstrates the difference:

Example: Java

Output:

As you can see above, in Java, every statement ends with a semicolon.

Example: Kotlin

Output:

On the other hand, in Kotlin, you don’t need a semicolon. The code works fine without it.

3. Code Length

Kotlin was created to fix some of the limitations that Java had. One big issue with Java is that it is very wordy, which means you have to write a lot of code to do simple things. Writing more code leads to more bugs and makes programs harder to manage. Kotlin solves this issue by letting you write less code, which makes it easier to read, reduces errors, and also saves both time and cost.

Example: Creating a User Class with Properties in Java

Output:

As you can see above, in Java, you need to write a constructor, getters, and extra code, which makes the code longer.

Example: Creating a User Class with Properties in Kotlin

Output:

On the other hand, a data class provides you with everything (constructor, getters, toString, etc.) in just one line. This makes the code look much shorter and cleaner.

4. Data Classes

In Java, when you create a data class, you have to write a lot of extra code, like the constructor, getters, and setters for the class to work properly. But in Kotlin, you don’t have to worry about that. You just need to use the data keyword, and Kotlin automatically creates a class that can hold data along with all the useful methods. This helps you to save time and effort. 

Example: Java

Output:

As you can see above, in Java, you must manually write the constructor, getters, setters, and also toString().

Example: Kotlin

Output:

On the other hand, in Kotlin, the data class automatically creates the constructor, getters, setters, equals, hashCode, and toString() for you in just one line of code.

5. Memory Management

In Java, you can use the static keyword for variables, methods, blocks, or even nested classes. This makes them belong to the class rather than individual objects. This helps them to save memory without creating an object. 

On the other hand, in Kotlin, there is no static keyword. You can use the object keyword to create a single instance inside a class, and that object acts like a static member. This provides you with direct access without needing to make an object every time.

Code: Java Example (using Static)

Output:

As you can see above, in Java, the static keyword makes a count and the methods belong to the same class, so that you don’t have to create an object to access them.

Code: Kotlin Example (using Object)

Output:

On the other hand, in Kotlin, you don’t have to use static. Instead of that, you can use the companion object, which works like a static member. You can directly access Counter.increment() or Counter.count without creating an object.

6. Type Conversion

Type conversion means changing one data type into another. In Java, some conversions happen automatically when you store a smaller type of value in a bigger one. In Kotlin, the conversion must be done explicitly by using functions such as toInt or toDouble.

Example: Java (automatic type conversion)

Output:

As you can see, the int is automatically converted into a double without needing extra code.

Example: Kotlin (explicit type conversion)

Output:

In Kotlin, you must use methods separately, like .toDouble(), .toInt(), .toString(), etc., to convert between types.

7. Smart Cast

In Java, although you already know that an object can be converted to a certain type, you still have to check its type and cast it manually. On the other hand, Kotlin makes your work easier with smart casts. If you check the type of an object using the is keyword, Kotlin will automatically treat it as that type, so that you don’t have to write extra code.

Code: Java Example (Manual Casting Required)

Output:

Example: Kotlin (Smart Cast)

Output:

In Java, you must write (String) obj even after you have checked the type. On the other hand, in Kotlin, the is check is enough. The compiler automatically treats it as a String.

8. Scripting

Scripting is basically a way to run code directly without needing the full setup of the project. Kotlin supports scripting, which means you can write small scripts and run them quickly to test or automate tasks. On the other hand, Java does not support scripting, and it always requires you to create full classes and methods before running any code.

Code: Kotlin (Scripting Supported)

Output:

Code: Java (No Direct Scripting)

Output:

Unlike Kotlin, you cannot just write Java code in a file and then run it. It requires a boilerplate (class + main method)

9. Null Checks

In Java, if you set a variable to null and then use it, you often run into the NullPointerException (NPE), which has frustrated many developers for years. On the other hand, in Kotlin, the variables are non-nullable by default. This means that you cannot just assign null values to them unless you specifically mention that they are null. You do this by adding a ? to the type. For example:

var message: String? = null
var cityName: String? = null

In this way, Kotlin helps you to avoid the unexpected NPEs, since the compiler will catch the problem even before the code runs.

10. Jetpack Compose

Kotlin works seamlessly with Jetpack Compose. Jetpack Compose is a modern toolkit from Google that is used for building UIs. It supports features like coroutines and is designed to work smoothly with both Compose and the older view-based UI system. Google has declared Kotlin as the primary language for Android development. On the other hand, Java does not support Jetpack Compose or those modern extensions, which means that developers using Java won’t be able to access them.

Future of Android Development Using Java vs Kotlin

When you look at the future of Android development using Java and Kotlin, Kotlin has become the preferred choice because it is modern, concise, easy to understand, and officially supported by Google as the primary Android language. It consists of features like null safety, coroutines, and Jetpack Compose, which help developers write cleaner and faster apps with fewer bugs.

Java, on the other hand, has been around for decades and continues to power many existing Android applications. Its strong community support and long history make it a reliable choice, but it lacks the modern tools and updates that Kotlin offers.

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Conclusion

Before we conclude, when you compare Kotlin vs Java, both these languages have their own strengths. Java has been around for many years now, is highly reliable, and still powers many applications. But Kotlin, on the other hand, is modern, less complex, and consists of features that make development faster and safer. With the official support from Google and tools like Jetpack Compose, Kotlin is clearly the preferred choice. Although both these languages can give you a strong edge, Java is great for older projects, while Kotlin is leading the way forward.

If you want to pursue your career as an Android developer, explore our Java Interview Questions and enroll in our Java Free Course.

Kotlin vs. Java: What’s the Difference? – FAQs