J0 Language

Novice programmers find Java hard because in order to write any working program, they need to know about classes, methods, and confusing keywords and syntax: static, void, etc.

J₀ (pronounced “J-zero”) solves this problem by letting programmers write methods and statements outside any class. Yet J₀ keeps all of the power of Java too: any legal Java program is a legal J₀ program.

An example program (click on it to toggle between the J0 and Java versions):

J₀ code:

{ println("Please enter your name:"); print("Name: "); String name = readLine(); println("Hello, " + name + "!"); }

Notice that the programmer doesn't have to define classes or methods in order to get started. Some helpful static methods like println are also automatically imported. Now click on this text to see the equivalent Java code.

Java code:

import java.io.*;


public class NameReader {
    public static void main(String[] args) {
	try {
	    BufferedReader reader =
		new BufferedReader(new InputStreamReader(System.in));
	    System.out.println("Please enter your name:" );
	    System.out.print("Name:");
	    String name = reader.readLine();
	    System.out.println("Hello, " + name + "!");
	} catch (IOException ioe) {
	    System.out.println(ioe);
	}
    }
}

Even for this simple program, Java requires the programmer to declare a class and a main method, to create complex objects, and to handle exceptions. The extra code you have to write in Java is highlighted in red. We don't think you should have to explain all this code to a novice programmer.

Download

The J₀ compiler is freely available for public download.

Credits

J₀ was developed at Cornell University using the Polyglot extensible Java compiler framework. The major contributors are:

Andrew Jonas
Daniel Lee
Andrew Myers

J0

A Java extension for beginning (and advanced) programmers

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Credits

J₀