java-magic 0.1.4

Magic cell para ejecutar Java de forma interactiva en Jupyter y Colab

Jupyter Java Magic

A lightweight Jupyter Notebook extension to write, compile, and execute Java code directly inside cells. It features automatic Google Colab setup and real-time interactive console input support (Scanner, System.in).

🛠️ Installation

pip install java-magic

🚀 Quick Start

1. Load the extension In your first notebook cell, load the magic:

%load_ext java_magic

2. Run standard Java code You don't even need a main class wrapper for simple snippets; the extension handles it automatically:

%%java
System.out.println("Hello from Jupyter!");

💡 Tip: Syntax Highlighting By default, Jupyter notebooks might not highlight Java code inside custom magic cells. To enable syntax highlighting, simply add %%js right next to the magic command like this:

%%java %%js
System.out.println("This code will be colored!");

3. Run interactive Java code If the extension detects Scanner or System.in, it automatically switches to an interactive terminal loop: (Tip: Add %js to )

%%java %%js
import java.util.Scanner;

Scanner scanner = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = scanner.nextLine();
System.out.println("Hello, " + name + "!");

4. Multi-cell Execution You can define a class in one cell and use it in another!

   Cell 1: Define a class

%%java %%js
package math;

/**
 * Clase de utilidad para operaciones matemáticas básicas.
 */
public class Calculadora {

    /**
     * Suma dos números enteros.
     * @param a El primer operando.
     * @param b El segundo operando.
     * @return La suma de a y b.
     */
    public static int sumar(int a, int b) {
        return a + b;
    }
}

Cell 2: Use the class

%%java %%js
import math.Calculadora;

int x = 10;
int y = 25;
int resultado = Calculadora.sumar(x, y);

System.out.println("El resultado de la suma es: " + resultado);

📚 Generate Documentation

You can easily render interactive HTML documentation right inside your notebook using the %javadoc magic command:

%javadoc math/Calculadora.java

⚙️ Configuration

By default, generated .java files are kept in your directory. To change this behavior, you can configure the extension:

%config JavaMagics.remove_java_file = True

To use %%javadoc set remove_java_file to False, since it needs the .java file to generate the documentation.

🧠 Technical Details & Architecture

When you run a cell, the extension creates physical .java and .class files in your environment's current working directory (e.g., Google Colab's /content). You can verify they exist by running:

!ls *.java *.class

How it differs from IJava Unlike the IJava kernel, this extension is not a continuous REPL. State is not saved: Variables declared in one cell (e.g., int x = 5;) do not persist in memory for the next cell.

📄 License MIT