Important Difference : Kotlin vs Java

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Kotlin vs Java

Kotlin is a statically typed language developed by JetBrains similar to Java, Most of the developers starts using Kotlin for developing Android Applications. This is evident from the fact that Android Studio comes with inbuilt support for Kotlin like it has for Java.

The Question arises that we should switch to Kotlin?
– Before making any choice we should understand the distinction between the two programming languages.

Checked Exceptions

This is the major difference here between Java & Kotlin, Kotlin has eliminated the checked exceptions. Therefore, there is no need to catch or declare any exceptions.
Developer has to use try/Catch blocks in Java to handle the checked exceptions in the code then the omission made by Kotlin can be consider a welcome change.However, it’s the opposite if the developer believes that checked exceptions encourage error recovery and the creation of robust code.

Code Conciseness

Comparing a Java class and Kotlin class performing the same task demonstrates the conciseness of Kotlin code. Result – Kotlin class has less code than java class
For example, a particular segment where Kotlin can significantly reduce the total amount of boilerplate code is findViewByIds.
Kotlin Android Extensions allows us to import a reference to a View into the Activity file. This allows for working with that View as if it was part of the Activity.

Data Classes

Big Projects needs large number of classes which are meant to hold data and a developer needs to write a lot of boilerplate code in java
Usually, a developer needs to define a constructor and several fields to store data, getter setter methods for each field, toString(), hashCode(), functions.
But Kotlin has a very easy way of handle all such classes. A developer only needs to include the data keyword in class definition and rest of the things will be taken care by compiler itself.

Extension Functions

Kotlin has a new functionality extension functions where developers can extend a class via extension functions. These functions, although available in other programming languages like C#, but not available in Java.
There is an easy way of creating extension functions in Kotlin.we have to Prefix the name of the class that needs to be extended to the name of the function being created. In order to call the function on the instances of the extended class, one needs to use the ‘.’ notation.

Higher-Order Functions and Lambdas

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

Kotlin can use of a range of function types for representing functions because of statically typed programming language. Moreover, it comes with a set of specialised language constructs, such as the lambda expressions.

Implicit Conversions

Kotlin has no support for implicit conversion for numbers. On the other hand Java has support for implicit conversions, where smaller types can convert into bigger types. Whereas Kotlin can perform only explicit conversion in order to achieve the conversion.

Inline Functions

Variables can be re accessed in the body of the function are known as closures. Making use of higher-order functions can impose several runtime penalties. Every function in Kotlin is an object and it captures a closure.

Both classes and function objects call for memory allocations. These along with virtual calls introduce runtime overhead. One such example is the lock() function.

Unlike Kotlin, Java doesn’t provide support for inline functions. Nonetheless, the Java compiler is capable of performing inlining using the final method. Because sub-classes cannot override final methods . Also, calling a final method can resolved at compile time.

Native Support for Delegation

In object-oriented programming, delegation refers to evaluating a member of one object (the receiver) in the context of another original object (the sender). Kotlin supports composition over inheritance design pattern by means of the first-class delegation, also known as implicit delegation.

Class delegation is an alternative to inheritance in Kotlin. This makes it possible to use multiple inheritances. This delegated properties can prevent the duplication of code in Kotlin.

Non-private Fields

Encapsulation is essential in any program for achieving a desirable level of maintainability.

Non-private fields or public fields in Java are useful in scenarios where the callers of an object need to change accordingly to its representation. Kotlin doesn’t have non-private fields.

Kotlin simply forces access to a field through its getter and setter, so there is no need to give the field more visibility than private to be able to access it.

Null Pointer Safety

Java lets developers to assign a null value to any variable. However, if they try to use an object reference that has a null value, then it throws the NullPointerException!

Kotlin has all types are non-nullable by default. If developers try to assign or return null in the Kotlin code, it’ll fail at compile time. However, there’s a way around. We can assign a null value to a variable in Kotlin, it is required to explicitly mark that variable as nullable. by adding a question mark after the type, for example:

val number: Int? = null

Thus, there are no NullPointerExceptions in Kotlin. If you do encounter such an exception in Kotlin then it is most likely that either you explicitly assigned a null value or it is due to some external Java code.

Smart Casts

It is mandatory to check type before cast an object in Java.

But Kotlin comes with the smart casts feature, which automatically handles such redundant casts. You don’t need to cast inside a statement provided it is already checked with the ‘is operator’ in KoMost of the developers starts using Kotlin for developing Android Applications.tlin.

Static Members

In the Java Programming Static is used for memory management mainly. We can apply static keyword with variables, methods, blocks and nested classes but Kotlin has no provision for static members.

It will create only one instance of the static member and share across all instances of the class.

Support for Constructors

Kotlin class can have one or more secondary constructors in addition to a primary constructor. Developer has to include the secondary constructors in the class declaration.

Ternary Operator

Java has a ternary operator. The Java ternary operator simply works like a basic if statement. It consists of a condition that evaluates to true or false.

Moreover, the Java ternary operator has two values. It will return only on value on the basis of conditions. The syntax for the Java ternary operator is:

(condition) ? (value1) : (value 2)


Java used in the general purpose programming on the other side more and more developers and organizations are adopting Kotlin for rapidly developing Android applications.

Both Java and Kotlin have their own advantages over the other. The debate about which of the two is the greatest has just started, and it is not likely to be over anytime soon.

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Written by 

Hi, I am a Software Intern in Knoldus Inc. with experience in technologies like Java Programming, SpringBoot. I am always ready to learn new technologies. My hobbies are watching web series and playing games.