Difference between Java and Kotlin in Android with Examples

Kotlin

KOTLIN is a cross platform, statically types, general purpose programming language with type inference. KOTLIN is designed to interoperate fully with java but type inference allows its syntax to be more concise.KOTLIN is sponsored by JetBrains and Google through the Kotlin Foundation.

Java

JAVA is an Object Oriented Programming Language developed by JAMES GOSLING and colleagues at SUN MICRO SYSTEMS in 1991.The language was initially called OAK. It was developed as a full fledged programming language in which one can accomplish the same sorts of tasks and solve the similar problems that one can do in other programming languages such as BASIC,C++ etc.

Using Kotlin over Java language in Android

The most important reason for introducing Kotlin to Android advancement was to decrease the number of lines of code and make development more convenient. Everything that can be done utilizing Java can be done utilizing Kotlin for Android development. 

For example:

• No need of findViewByIds: It is used to find the first descendant view with the given ID. 
  Java
  TextView text = (TextView) findViewById(R.id.textView); 
  text.setText(“Hello World”); 

  Kotlin
  textView.setText(“Hello World”)

• Free from Null Pointer Exception
  NullPointerExceptions are a tremendous source of disappointment for Java designers. In Kotlin, all sorts are non-nullable (incapable to hold null value) by default. If the code tries to use or return null in Kotlin, compile time error is shown. 
  var a: String = “abc” // compilation error 
  a = null 
• Data Class: We often create classes to hold some data in it. In such classes, some standard functions are often derivable from the data. In Kotlin, this type of class is known as data class and is marked as data.

data class User(val name: String, val age: Int)

There are many differences in both these languages according to their features

Features	Kotlin	Java
1. Extension Functions	It is already available in Kotlin	In java, we need to create class
2. Null Safety	It is available in Kotlin	It is not available in Java
3. Static Members	Kotlin doesn’t have a static member for a class	It is available in Java
4. String Templates	Yes, there are two types of string literals in Kotlin	It is available in Java too but it doesn’t support expression like Kotlin
5. Wildcard Types	It is not available in Kotlin	Available in Java
6. Smartcasts	Available in Kotlin	Not Available in Java
7. No Checked Exceptions	Kotlin removed exceptions entirely	It is problematic in Java
8. Operator Overloading	Kotlin allows users to provide a way to invoke functions	Operators are tied to particular Java Types
9. Constructors	It has primary constructor and secondary constructor	Constructors can be used to take parameters to initialize attributes
10. Type System	It gives nullability support, type inference, and universal guards	There are other kinds of reference types related to the basic concept of class

Despite all the differences between the two languages, Java and Kotlin are 100% interoperable. You can call Kotlin code from Java, and you can call Java code from Kotlin. So it’s possible to have Kotlin and Java classes side-by-side within the same project, and everything will still compile.