Differences between "beginner" Java and Kotlin

What is Kotlin

--Kotlin is a language that runs on the JVM created by JetBrains. --Kotlin is fully interoperable with Java. You can write a class in Java, a class that inherits it in Kotlin, and a class that inherits it in Java. --You can write additional development in Kotlin for a project written in Java, which makes it easy to introduce. --Google has announced official Kotlin support for Android.

Variable declaration

Use val for constants and var for mutable variables.


String str = "String";
final int value = 0;


var str: String = "String"
val value = 0

Since type inference is possible in Kotlin, variables can be defined by omitting the type. No semicolon is needed.

if statement


String value = bar < 10 ? "abc" : "xyz";


 var value = if (bar < 10) "abc" else "xyz"

You can directly assign the result in the if or else block.

for statement


for(int num : numbers)
for(int i = 0; i< 4; i++)


for (num in numbers)
for (i in 0..3)

Kotlin uses in.



public int add(int a, int b) 
    return a + b;


fun add(a:Int, b:Int): Int {
    return a + b


In the case of Kotlin, if the access modifier is omitted, it is treated as public. Furthermore, if the return type allows the compiler to perform type inference, it is possible to omit the definition of the return type.

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