What Programming Languages Are Used for the Java Compiler and JVM?

What languages are used to write the Java compiler (javac) and the Java Virtual Machine (JVM)?

The Java compiler, known as javac, and the Java Virtual Machine (JVM) play critical roles in the Java programming ecosystem. Understanding the languages used to implement these components provides insights into their architecture and performance.

// Sample code snippet to show a simple compilation process in Java
public class Example {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}  
// To compile the above code using javac:\n// > javac Example.java\n// To run the compiled code using the JVM:\n// > java Example

Causes

• javac is primarily written in Java, utilizing the language's features for parsing and compiling Java source code.
• The JVM is predominantly implemented in C and C++, which allows for low-level system interaction and platform independence.

Solutions

• To understand how javac operates, one can explore its source code available in the OpenJDK repository, where it leverages Java for its entire compilation process.
• The JVM's implementation benefits from the efficiency of C/C++, enabling optimized performance across different hardware and operating systems.

Mistake: Assuming the JVM is written only in Java.

Solution: Recognize that the JVM is primarily implemented in C/C++, designed for performance optimization.

Mistake: Neglecting to refer to open-source resources for learning about javac or JVM functionality.

Solution: Utilize the OpenJDK documentation and source code to better understand the compiler's workings.