Help with Lists

[Darkzombies]

Basically what I want is a program that holds information in neat lines as it is added. Scrolls when it gets to the bottom. I am trying to create it because it can be used for many things, like a text adventure. While I'm at that, I'd also like to know how I can have an input using graphics and not the output. It won't compile or print anything onto the screen, in addition to that there are parts that just don't seem very optimized.

import java.applet.Applet;
import java.awt.*;
import javax.swing.JFrame;


public class Main extends Applet{
	
	public static boolean gameOver = false;
	public static int gameState = 0;
	public static TextWall tw = new TextWall();
	
	public void paint(Graphics g){
		
	}
	
	public static void main(String[] args){
		
		JFrame frame = new JFrame();
		Main a = new Main();
		frame.getContentPane().add(a, BorderLayout.CENTER);
		frame.setSize(new Dimension(1360,768));
        frame.setVisible(true);
        tw.addInfo("Test");
		tw.repaint();
        
        //Main Loop
        
        while(!gameOver){
        	if(gameState == 0){ //Main Menu
        		
        	} else if(gameState == 1){
        		
        	} else if(!(gameState == 1 || gameState == 0)){

                           //Example

        		tw.addInfo("Please enter a valid number");
        		tw.repaint();

                           //Example
        	}
        }
	}
}

import java.awt.Graphics;
import java.util.List;


public class TextWall {
	
	private List<String> info;
	private Graphics g;
	private int lastY = 0;
	
	public TextWall(){
		
	}
	
	public void addInfo(String s){
		info.add(s);
	}
	
	public void removeInfo(int i){
		if(info.contains(i)){
			info.remove(i);
		}else{
			System.err.println("String was not found.");
		}
	}
	
	public List<String> getInfo(){
		return info;
	}
	
	public void repaint(){
		for(int x = 0; x > info.size(); x++){
			g.drawString(info.get(x), 100, lastY * 100);
			lastY ++;
		}
	}
}

Exception in thread "main" java.lang.NullPointerException
at TextWall.addInfo(TextWall.java:16)
at Main.main(Main.java:23)

[JosAH]

You're not creating a List<String> in that class for your 'info' reference variable; the constructor is a nice place to do so, i.e.

public TextWall(){
   info= new ArrayList<String>();
}

kind regards,

Jos

[Darkzombies]

That took care of the error, but it still doesn't print anything to the screen, so I moved

for(int x = 0; x >= tw.getInfo().size(); x++){
			g.drawString(tw.getInfo().get(x), 100, lastY * 100);
			lastY ++;
		}

to the paint method, but it still doesn't draw anything. I'm assuming I need a repaint in my main loop but my main loop is in my static main method, and that doesn't follow OOP. The only solution I can think of is to make a new class for my main loop, or stuff it into the textwall class. Is this an efficient solution?