Java Examples

Basic Measurement

Given Main.java:

public class Main {
    static double compute(int n) {
        double sum = 0;
        for (int i = 0; i < n; i++)
            sum += Math.sin(i) * Math.cos(i);
        return sum;
    }

    public static void main(String[] args) {
        int n = args.length > 0 ? Integer.parseInt(args[0]) : 1000000;
        System.out.println(compute(n));
    }
}

codegreen measure java Main.java -- 1000000
codegreen measure java Main.java -g fine --export-plot energy.html

How It Works for Java

1. Tree-sitter parses the Java source and identifies method definitions
2. Checkpoint calls are injected at method enter/exit points
3. The instrumented source is compiled with javac
4. The compiled class runs with the CodeGreen Java runtime on the classpath
5. Energy data is collected via the NEMB C++ backend

Known Limitations

• Java filename must match the public class name
• JNI bridge for NEMB has known issues with some JVM configurations
• Best results with simple single-file programs