Kotlin vs. Java: Which Language Would You Choose For Android App Development?
                     Kotlin vs. Java
Created by Space-O Technologies
1. Extension functions
Kotlin Java
● Available in Kotlin. Extensions are ● In Java, we need to create a new 
useful as they allow developers to class to extend the functionality of 
add methods to classes without the existing class, so from now 
making changes to their source users can use a newly created 
code. class everywhere to use the 
extended functionality.
2. Null safety
Kotlin Java
● Available. Kotlin type of system has ● Not available. In fact, 
inbuilt null safety. NullPointerException is mainly 
responsible for the development 
errors of Android and Java.
3. Static members
Kotlin Java
● In Kotlin, we can use the ● Available in Java. It is used for 
companion object to create static memory management mainly. One 
members of the class. An object can apply java static keyword with 
declaration inside a class can be variables, methods, blocks and 
marked with the companion nested class.
keyword.
4. String templates
Kotlin Java
● Yes, there are two types of string ● Available in Java too, but it doesn’t 
literals in Kotlin such as escaped support expression like Kotlin.
string and raw string.
● Kotlin string template also supports 
expression.
5. Coroutines
Kotlin Java
● In Kotlin, coroutines are ● In Java, users have two different 
concurrency design pattern that can options such as RxJava and Project 
be used to simplify code on Android Loom. RxJava is a library for 
that performs asynchronously. composing asynchronous and 
Coroutines were added to Kotlin in event-based programs using 
1.3 version and they are based on observable sequences and Project 
established concepts from other Loom supports a high-throughput, 
languages. lightweight concurrency model in 
Java.
6. Wildcard-types
Kotlin Java
● No, Kotlin doesn’t have any ● Available in Java. Wildcard in 
wildcard-types. But it has two other general code means (?) that 
things, including declaration-site represents an unknown type. It can 
variance and type projections. be used in different situations.
7. Smart casts
Kotlin Java
● Yes, this feature is available in ● No, it is not available in Java. 
Kotlin. It helps Kotlin compiler to However, to know the types in 
track conditions inside if Java, we can use something like 
expression. If the compiler finds a instanceof to check the type and 
variable that is not null of type then cast it to the right type.
nullable, the compiler allows 
accessing the variable.
8. Lazy-Loading
Kotlin Java
● Yes, it is available in Kotlin. It ● This feature is not available in Java.
mainly decreased startup time that 
is useful when using Kotlin for app 
development.
9. No checked exceptions
Kotlin Java
● Kotlin removed exceptions entirely ● In Java, the checked exceptions 
in order to minimize verbosity and feature is a problem as it causes 
improve type-safety. empty catch blocks.
10. Operator overloading
Kotlin Java
● Yes, Kotlin allows users to provide ● In Java, operators are tied to 
a way to invoke functions in order particular Java types. For instance, 
to do an arithmetic operation, String and numeric types in Java 
equality checks or comparison on can make use of + operator for 
whatever object we want, through concatenation and addition. 
symbols like +, -, /, *, %, . Another Java type can’t reuse this 
operator.
11. Constructors
Kotlin Java
● Kotlin only has a primary ● In Java, constructors can be used 
constructor and one or more to take parameters that is used to 
secondary constructors. Talking initialize attributes.
about primary constructor, it is the 
part of the class header and it goes 
after the class name.
12. Type System
Kotlin Java
● Kotlin typing system is mainly ● In Java, the type system involves 
designed to give users nullability not only classes and primitive 
support, type inference, and types. Other kinds of reference type 
universal guards. are related to the basic concept of a 
class; however, it varies in some 
way, and are mainly treated in a 
special way by Java or the JVM.
13. Collections
Kotlin Java
● In Kotlin, the order of collections is ● In Java, a collection is a group of 
similar as in Java: Collection, List individual objects that showed as a 
and Set. The only difference that single unit. Java has a collection 
you can see is – it’s divided framework, defining several classes 
between mutable and immutable and interfaces to represent a group 
types. Mutable types provide of objects as a single unit.
methods to change contents 
whereas immutable types don’t.
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