This paper aims to compare methods for the improvement of the application's code conversion from Java to Kotlin, uncovering results and problems regarding each technique. An application had been created. And by applying 3 different ways of converting the Java code conversation to Kotlin, each method had been then compared in terms of its effectiveness. Those 3 ways comprised: 1) conversion with a tool 2) conversion by creating a new fle with an old project, and 3) conversion by creating a new fle with a new project. However, the functions of the application must remain the same. Findings from this research study revealed problems and factors that can have an impact on the selection of code conversation from Java to Kotlin