Java and Kotlin are the two primary programming languages utilized in Android app development. Java has long been the traditional choice for Android development due to its widespread usage and robust ecosystem. However, Kotlin, introduced by JetBrains, has emerged as a popular alternative. Kotlin's concise syntax, enhanced safety features, and seamless interoperability with Java have contributed to its rapid adoption among Android developers. While Java remains prevalent, many developers favor Kotlin for its modern features and improved developer productivity. The combination of Java and Kotlin allows developers to leverage the strengths of each language, resulting in efficient and feature-rich Android applications.