How is the source code of Java transformed into an executable file during the build process?

Java source code (.java files) is first compiled by the javac compiler into bytecode, which is stored in .class files. This bytecode is not machine code specific to any processor but is an intermediate representation executed by the Java Virtual Machine (JVM).

The build process typically looks like this:

1. Compilation: javac MyClass.java → MyClass.class
2. Optional: packaging .class files into a .jar archive
3. Running: JVM loads the .class files and interprets or compiles them into machine code at runtime (JIT compilation).

Thus, transforming source code into an executable file is a compilation into bytecode, not into a native executable. JVM ensures portability and security of execution.