Introduction

1. What is Kotlin?

Kotlin is a modern programming language mainly used for Android app development.

It is simple, safe, and works with Java.

Simple Kotlin Program

fun main() {
    println("Hello Kotlin")
}

Output

Hello Kotlin

Explanation

Code	Meaning
`fun`	Used to create a function
`main()`	Starting point of a Kotlin program
`println()`	Prints output on the screen

2. Kotlin Features

Kotlin has many useful features.

Feature	Simple Meaning
Concise code	Less code compared to Java
Null safety	Helps avoid null pointer crash
Type inference	Kotlin detects data type automatically
Java interoperability	Kotlin can use Java code
Data classes	Easy way to create model classes
Extension functions	Add new functions to existing classes
Coroutines	Used for background tasks
Smart cast	Kotlin automatically converts checked types

Example: Kotlin is Concise

Java Code

String name = "Mahesh";
System.out.println(name);

Kotlin Code

val name = "Mahesh"
println(name)

Simple meaning:

Kotlin does the same work with fewer lines and cleaner syntax.

3. Kotlin vs Java

Point	Java	Kotlin
Code length	More code	Less code
Null safety	Manual handling	Built-in null safety
Semicolon	Usually used	Not required
Variables	`final`, normal variable	`val`, `var`
Data class	Need constructor, getter, setter	One line
Android support	Supported	Preferred
Functional features	Limited	Strong support
Coroutines	Not built-in	Easy support

Example: Model Class

Java

public class User {
    private String name;
    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}

Kotlin

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

Simple meaning:

Kotlin removes boilerplate code like constructor, getter, and setter.