What is Kotlin Language?

/* Java Code */
static int num1, num2; //explicit declaration
num1 = 20; //use the variables anywhere
num2 = 30;

/* Kotlin Code*/
val a: Int
val b: Int
a=5
b=10

/* Kotlin Code*/
/* Simple Hello Word Example*/

//optional package header
package hello 

//package level function, which return Unit and takes an array of string as parameter
fun main(args: Array < String > ) { 
 val scope = “world”
 println(“Hello, $scope!”) //semicolons are optional, have you noticed that? :)
}

Filename extensions of the Java are .java, .class, .jar but on the other hand filename extensions of the Kotlin are .kt and .kts.

Benefits of Kotlin Language

• Kotlin compiles to JVM bytecode or JavaScript - Like Java, Bytecode is the compiled format for Kotlin programs also. Bytecode means Programming code that, once compiled, is run through a virtual machine instead of the computer’s processor. By using this approach, source code can be run on any platform once it has been compiled and run through the virtual machine. Once a kotlin program has been converted to bytecode, it can be transferred across a network and executed by JVM(Java Virtual Machine).

• Kotlin programs can use all existing Java Frameworks and Libraries - Yes, it's true that Kotlin programs can use all existing java frameworks and libraries, even advanced frameworks that rely on annotation processing. The main important thing about kotlin language is that it can easily integrate with Maven, Gradle and other build systems.

• Kotlin can be learned easily and it is approachable. It can be learned easily by simply reading the language reference.The syntax is clean and intuitive(easy to use and understand). Kotlin looks a lot like Scala but is simpler.

• Kotlin is Open Source and it costs nothing to adopt.

• Automatic conversion of Java to Kotlin - JetBrains integrated a new feature into IntelliJ which converts Java to Kotlin and saves a huge amount of time. And it also saves us to retype mundane code.

• Kotlin’s null-safety is great - Now get rid of NullPointerExceptions. This type of system helps us to avoid null pointer exceptions. In Kotlin the system simply refuses to compile code that tries to assign or return null. Consider the following example -

val  name: String = null  // tries to assign null, won’t  compile.
 
fun  getName() : String = null  // tries to return null, won’t  compile.

• Code reviews are not a problem - Kotlin is much more focuses on readable syntax so code reviews are not a problem, they can still be done by those team members who are not familiar with the language.

Features of Kotlin Language

• The billion dollar mistake made right. As already mentioned above that Kotlin avoids the null pointer exception. If we try to assign or return null to a variable or function respectively, then it won’t compile.

val name: String? = null    //assigned  null and it will compile  also.
 
fun getName() : String? = null //returned null and it  will compile too.

/* won’t compile */ 
  val name: String? = null
  val len = name.length 

/* correct way */ 
  val name: String? = null 
  val len = name?.length

• Versatile
  
  
  
  
  

• Lean Syntax and Concise - One liner functions take one line, simple structs/JavaBeans can also be declared in one line. Real properties generate getters and setters behind the scenes for Java interop. And Adding the data annotation to a class triggers autogeneration of boilerplate like equals, hashCode, toString and much more.

/*  Java program */ 

public class Address {
  
   private String street;

   private int streetNumber;

   private String postCode;

   private String city;

   private Country country;

   public Address(String street, int streetNumber, String postCode, String city, Country country) {

       this.street = street;

       this.streetNumber = streetNumber;

       this.postCode = postCode;

       this.city = city;

       this.country = country;

   }

   @Override
   public boolean equals(Object o) {
       if (this == o) return true;

       if (o == null || getClass() != o.getClass()) return false;

       Address address = (Address) o;

       if (streetNumber != address.streetNumber) return false;

       if (!street.equals(address.street)) return false;

       if (!postCode.equals(address.postCode)) return false;

       if (!city.equals(address.city)) return false;

       return country == address.country;
   }

   @Override
   public int hashCode() {
       int result = street.hashCode();

       result = 31 * result + streetNumber;

       result = 31 * result + postCode.hashCode();

       result = 31 * result + city.hashCode();

       result = 31 * result + (country != null ? country.hashCode() : 0);

       return result;

   }

   @Override

   public String toString() {

       return "Address{" +

               "street='" + street + '\'' +

               ",     streetNumber=" + streetNumber +

               ",     postCode='" + postCode + '\'' +

               ",     city='" + city + '\'' +

               ",     country=" + country +

               '}';

   }

   public String getStreet() {

       return street;

   }

   public void setStreet(String street) {

       this.street = street;

   }

   public int getStreetNumber() {

       return streetNumber;

   }

   public void setStreetNumber(int streetNumber) {

       this.streetNumber = streetNumber;

   }

   public String getPostCode() {

       return postCode;

   }

   public void setPostCode(String postCode) {

       this.postCode = postCode;

   }

   public String getCity() {

       return city;

   }

   public void setCity(String city) {

       this.city = city;

   }

   public Country getCountry() {

       return country;

   }

   public void setCountry(Country country) {

       this.country = country;

   }

}

/*  Kotlin Program */

data class Address(var street:String,

       var streetNumber:Int,

       var postCode:String,

       var city:String,

       var country:Country)

Difference Between Kotlin And Java

• Null Safety - As already mentioned in above section that Kotlin avoids NullPointerException. Kotlin fails at compile-time whenever a NullPointerException may be thrown.

• Data Classes - In Kotlin there are Data Classes which leads to autogeneration of boilerplate like equals, hashCode, toString, getters/setters and much more...
  
  
  Continue Reading About Kotlin V/s Java At: XenonStack.com/Blog

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Use Of Reactive Programming & Functional Programming

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