Why is a virtual machine needed in the context of Android app development?

A virtual machine (VM) in Android (Dalvik or ART) is necessary for executing bytecode compiled from Java/Kotlin. It provides the following key advantages:

• Cross-platform compatibility: Code written in Java/Kotlin is compiled into bytecode, which can run on various hardware architectures of Android devices without recompilation for each architecture. The VM interprets this bytecode.
• Security: The VM isolates applications from each other and from the operating system, preventing unauthorized access and malicious actions. Each application runs in its own process with a separate VM.
• Resource management: The VM manages memory (garbage collection) and threads, simplifying development and preventing memory leaks or crashes due to improper resource management.
• JIT/AOT compilation:
  • Dalvik: Used Just-In-Time (JIT) compilation, which compiles bytecode into native code at runtime.
  • ART: Uses Ahead-Of-Time (AOT) compilation, which compiles bytecode into native code once during app installation, providing higher performance and faster execution.

In summary, the VM allows developers to write code in high-level languages without worrying about hardware specifics, and ensures safe and managed execution of applications on devices.