Kotlin is a statically typed programming language developed by JetBrains. Like the Java language, Kotlin has become a great choice for developing Android applications. This can even be seen from the fact that Android Studio comes with built-in Kotlin support, as well as Java support.

Kotlin vs Java

So the question is, is it worth the developer to switch to Kotlin with Java or not? Of course, it depends on the preferences of the developer. However, before switching, it is important to understand the difference between the two programming languages.

Checked Exceptions

One of the main differences between Java and Kotlin is that there are no conditions for checked exceptions. Therefore, there is no need to catch or make any exceptions.

If a Java developer thinks using try / catch code in the code is annoying, then the omission made by Kotlin can be considered a desired change. However, the opposite will be if the developer believes that checked exceptions are needed, contributing to error recovery and creating reliable code. In this case, this can be considered a plus and minus for Kotlin, depending on the development approach.

Code brevity

A comparison of the Java class with the equivalent Kotlin class demonstrates the conciseness of the Kotlin code. For the same operation that is performed in the Java class, the Kotlin class requires less code.

For example, a specific segment where Kotlin can significantly reduce the overall amount of standard code is findViewByIds.

Kotlin extensions on Android let you import a View link into an Activity file. This makes it possible to work with this view as if it were part of an Activity.

This clearly can be attributed to the advantages of Kotlin.


Processes that intensively load the processor and network I / O usually use lengthy operations. The calling thread is blocked until the entire operation is completed. Since Android is single-threaded by default, the user interface of the application is completely blocked as soon as the main thread is blocked.

The traditional solution to this problem in Java is to create a background thread for long or intensive work. However, managing multiple threads leads to increased complexity, as well as errors in the code.

Kotlin also allows you to create additional threads. However, there is a better way to manage intensive operations in Kotlin, known as corograms or coroutines. Kotlin’s coroutines are stack-free, which means they require less memory use than regular threads.

Coroutines can perform lengthy and intensive tasks, pausing execution, not blocking the flow, and then resuming execution after some time. This allows you to create non-blocking asynchronous code that looks like synchronous in operation.

The code using corutine is not only clear, but also concise. Moreover, coroutines allow you to create elegant additional styles of asynchronous non-blocking development, such as async / await.

All this also clearly applies to the advantages of Kotlin.

Data classes

In full-size projects, there are usually several classes designed exclusively for storing data. Although these classes have virtually no functionality, the developer needs to write a lot of standard Java code.

Typically, the developer should define a constructor and several fields for storing data, getter and setter functions for each of the fields, as well as the equals (), hashCode () and toString () functions.

Kotlin has a very simple way to create such classes. It is enough for the developer to include only the data keyword in the class definition, and that’s all – the compiler will take care of everything.

This convenience of creating classes, in the pros and cons for Kotlin, clearly shows in his favor.

Extension Functions

Kotlin allows developers to extend the class with new features using extension functions. These functions, although available in other programming languages ​​such as C #, are not available in Java.

Creating an extension function is easy in Kotlin. This is done by adding a prefix to the class name, which should be expanded to the name of the function being created. To call a function in instances of an extended class, you need to use the notation “.”

Higher Order Functions and Lambdas

A higher-order function is a function that takes other functions as parameters or returns a function. In addition, Kotlin functions are first class functions. This means that they can be stored in data structures and variables that can be passed as arguments and returned from other higher-order functions.

All this simply means that functions can work in all possible ways in conjunction with other non-functional values.

As a statically typed programming language, Kotlin uses a number of functional types to represent functions. Moreover, it comes with a set of specialized language constructs such as lambda expressions.

Anonymous functions and lambda expressions are also known as functional literals. These are functions that are not declared, but are passed as expressions.

Implicit Extensible Conversions

In Kotlin, there is no support for implicit extending transformations for data. Thus, smaller types cannot be converted to larger types. While Java supports implicit conversions, Kotlin requires an explicit conversion.

A number of developers perceive this as a minus of Kotlin.

Built-in functions

Variables that are accessed in the function body are called closures. The use of higher-order functions can significantly increase the computational time. Each function in Kotlin is an object, and it captures a closure.

Both classes and functors require memory allocation. They, along with virtual calls, require certain costs for execution time. This extra cost can be avoided by inserting lambda expressions into Kotlin. One such example is the lock () function.

Unlike Kotlin, Java does not provide support for built-in functions. However, the Java compiler is capable of embedding using the final method. This is because final methods cannot be overridden by subclasses. In addition, the final method call is resolved at compile time.

Such innovations are also perceived as Kotlin’s advantages.

Native delegation support

In programming terminology, Delegation is a process in which a receiving object delegates its operations to a second delegate object. Kotlin supports the design pattern composition on top of inheritance through first-class delegation, also known as implicit delegation.

Kotlin delegation is an alternative to inheritance. This mechanism allows to multiple inheritance. In addition, Kotlin’s delegated properties prevent code duplication.

Non-private fields

Encapsulation is necessary in any program to achieve the desired level of controllability.

Through encapsulation, the representation of an object can be established based on how the callers interact with it. In addition, you can change the view without having to change the callers if the public API remains unchanged.

Private fields in Java are useful in scripts where callers must change according to their presentation. This means that such fields provide an object representation to the caller. Kotlin has no non-private fields.

This is quite an interesting difference when comparing Kotlin and Java.

Zero security

One of the most notable issues for Java developers is NullPointerExceptions. Java allows developers to assign null to any variable. However, if they try to use an object reference with a null value, a NullPointerException is shown

Unlike Java, in Kotlin, all types are non-nullable by default. If developers try to assign or return null in Kotlin code, a crash will occur during compilation. However, there is a way around this point. To assign a null value to a variable in Kotlin, you must explicitly mark this variable as nullable. This is done by adding a question mark after the type, for example:

val number: Int? = null

Thus, in Kotlin there are no NullPointerException exceptions. If you encounter such an exception in Kotlin, then most likely you have either explicitly set it to null, or this is due to some external Java code.

Primitive types

There are 8 primitive data types, including char, double, float, and int. Unlike Kotlin, primitive type variables are not objects in Java. This means that they are not objects created from a class or structure.

Smart casts

Before an object can be cast in Java, you must definitely check the type. This is also true in scenarios where the object obviously needs to be cast.

Unlike Java, Kotlin has a smart cast function that automatically processes such redundant casts. You do not need to cast inside a statement if it has already been verified by the is statement in Kotlin.

Static Members

Kotlin has no static elements. However, in the Java programming language, the static keyword reflects the fact that the particular member with which this keyword is used belongs to the type itself, and not an instance of that type.

It just means that one and only one instance of this static member is created and used by all instances of the class.

Constructor Support

Kotlin classes, unlike Java classes, can have one or more secondary constructors, in addition to the primary constructor. This is done by including these secondary constructors in the class declaration.

Ternary operator

Unlike Kotlin, Java has a ternary operator. The ternary operator in Java acts as the basic if. It consists of a condition that is evaluated as true or false.

In addition, the ternary operator in Java has two meanings. Only one of them returns depending on whether the condition is true or false. The syntax for the Java ternary operator is:

(state) ? (value 1): (value 2)

Wildcard Types

In common code, ‘?’ represents an unknown type. This character is known as a wildcard. There are several options for using a wildcard, including as a field type, local variable, or parameter.

While the Java type system suggests using wildcards, Kotlin doesn’t. However, it has two other mechanisms – variability at the declaration level and type projection as an alternative.

This will be useful to consider when upgrading from Java to Kotlin.

Kotlin Annotation Libraries

In addition to providing support for existing Java frameworks and libraries, Kotlin also offers advanced annotation-based Java frameworks.

However, using a Java library in Kotlin that uses annotation processing requires adding it to the Kotlin project in a slightly different way than you would for a Java library that does not use annotation processing.

It is required to specify the dependency using the kotlin-kapt plugin. After that, you need to use the Kotlin annotation tool instead of annotation Processor.

Still confused? Here is the solution – interchangeability!

Obviously, some points are better implemented in Kotlin, while for others it is beneficial to use Java. For those who do not want to abandon either of the two leading programming languages ​​for Android development, fortunately, there is another way.

Regardless of all the differences between the two programming languages, they are fully compatible. Both Java and Kotlin are compiled into bytecode. This means that there will be no definite answer to “Kotlin vs Java” questions, because you can call Java code from Kotlin and vice versa.

This flexibility has two advantages. Firstly, it makes it easier to get started with Kotlin by gradually adding Kotlin code to a Java project. Secondly, both languages ​​can be used simultaneously in any Android application development project.


Despite the significant advantages of Kotlin, Java has gained the top in general-purpose development issues. On the other hand, more developers and organizations are introducing Kotlin to quickly develop Android applications.

Both Java and Kotlin have advantages over each other. The discussion about which one is better for development has just begun, and it is unlikely to end in the near future. Questions of choice: “Why Java?”, “Why Kotlin?” Still remain. In any case, switching from Java to Kotlin will not be hard.