How to call Java code in Kotlin Application: Java and Kotlin Interoperability

Java is fully compatible with Kotlin . So to call java code in kotlin first write following java and kotlin code two separate file .

KotlinApplication.kt

fun main(args:Array<String>){

println("Kotlin Application Started ....... ");

var javaApplication = JavaApplication();

println("-------------------------------------------");

println("Navigating to Java Application  ....... ");

println("-------------------------------------------");

javaApplication.naivgateToJavaApplication();

}

JavaApplication.java

public class JavaApplication{

     public JavaApplication(){}

     public static void main(String []args){

    

     System.out.println("Java Application Started ..... ");

   

}

public void naivgateToJavaApplication(){

     System.out.println("Welcome in Java Application .......");

}

}

To Compile and run above two file there is two method . 

First Method to Compile and run java code in kotlin application 

Compile using kotlinc and Running using Kotlin

1 . Complie java file 

javac JavaApplication.java

2 .Running java file  

java JavaApplication

3.Compling kotlin file by setting class path of JavaApplication.class file 

kotlinc -cp . KotlinApplication.kt 

Note :-

After Compiling of KotlinApplication.kt  kotlinc compiler conventionally generate 

KotlinApplicationKt.class

by default  kotlinc compiler append Kt in suffix of kotlin file name. 

4. Now at last Runing KotlinApplicationKt.class by seting class path of JavaApplication.class file 

 kotlin -cp . KotlinApplicationKt

Output in Console ......

Second Method to Compile and run java code in kotlin application 

Complie and package into java jar using kotlinc and Runing  java jar using Java

Running with Java Jar using Java

1 .Compile java file 

javac JavaApplication.java

2 .Running java file 

java  JavaApplication

3.Compling kotlin file by setting class path of JavaApplication.class file 

kotlinc -cp . KotlinApplication.kt -include-runtime -d kotlinapplication.jar

4. Updating kotlinapplication.jar with JavaApplication.class file 

jar -uf KotlinApplication.jar JavaApplication.class

5. Running  KotlinApplication.jar file 

java -jar KotlinApplication.jar

Output in Console .....