ConsoleProgram.java

import java.util.*;

public class ConsoleProgram{

	private Scanner scanner;

	public static void main(String[] args){
		// Assume the class name is passed in as the first argument.

		if(args.length == 0){
			System.out.println("Please provide the name of the main class as an argument.");
			return;
		}

		String mainClassName = args[0];

		try{
			Class mainClass = Class.forName(mainClassName);
			Object obj = mainClass.newInstance();
			ConsoleProgram program = (ConsoleProgram)obj;
			program.run();
		} catch (IllegalAccessException ex) {
			System.out.println("Error in program. Make sure you extend ConsoleProgram");
		} catch (InstantiationException ex) {
			System.out.println("Error in program. Make sure you extend ConsoleProgram");
		} catch (ClassNotFoundException ex) {
			System.out.println("Error in program. Make sure you extend ConsoleProgram");
		}
	}

	public void run(){
		/* Overridden by subclass */
	}

	public ConsoleProgram(){
		scanner = new Scanner(System.in);

	}

	public String readLine(String prompt){
		System.out.print(prompt);
		return scanner.nextLine();
	}

	public double readDouble(String prompt){

		while(true){
			String input = readLine(prompt);
			try {
				double n = Double.valueOf(input).doubleValue();
				return n;
			} catch (NumberFormatException e){

			}
		}
	}

	public int readInt(String prompt){

		while(true){
			String input = readLine(prompt);
			try {
				int n = Integer.parseInt(input);
				return n;
			} catch (NumberFormatException e){

			}
		}
	}

}

HelloWorldjava

public class HelloWorld extends ConsoleProgram{

	public void run()
	{
		System.out.println("Hello world!");

		int x = readInt("Type in your favorite int: ");
		System.out.println(x);

		double d = readDouble("Type in your favorite double: ");
		System.out.println(d);
	}
}

How To Run

## Note you just compile as normal
## Then you run with `java` but also pass the name of the main class as the specific entry point as the first argument

$ javac HelloWorld.java
$ java HelloWorld HelloWorld
Hello world!
Type in your favorite int: 323
323
Type in your favorite double: 123.2
123.2

Seems pretty reasonable. I tested it against my server, and I will have to add support for optionally specifying the main class when there are multiple main() methods defined.

Would suggest you try to break up the long-lines in the final version.