Thread: Help with an object based level format

So I had to scrap my old tile based level format for an object based one so I could use arraylists. The first thing I need to figure out is how to execute Java code written in a text file. The reason I need this is because each object will be added to the arraylist one by one from the txt.

Example of what I want to execute as my test(in case it helps)
 
Level1.add(new GroundTileATop(10,10)
Level1.add(new GroundTileATop(40,10)

Sorry if this is a n00bish question, but I'm still sort of a beginner in Java, and I've never done anything like this before.

To execute java code, you need to compile it.
For java code to compile it must be in a class and a method for most cases.

A problem would be for the variables referenced in the code, they would be isolated from the variables in the program that is compiling and executing the java statements. You'd have to pass references to the local variables to the method in the code being created.

Can you explain what you are trying to do and why you think Java is the right language to do it in?

Well, I'm trying to write a list of objects in an external file to an arraylist, then place each object on the JPanel in order. I've got a tutorial I'm following for the actual placing that should work, but the problem is that the part of the tutorial that writes the list of objects to the arraylist is hardcoded. I absolutely can not hardcode much of anything, because 1) I want my engine to be as easily edited as possible, and 2) I may make other games based off of the same engine, so the less that's hardcoded, the less needs to be changed for a specific game.

Originally Posted by pbrockway2

If your intention is to create a bunch of GroundTileATop objects and add them to this Level1 thing (level1 would be a better name) then just do that. Have a text file containing the integer arguments and read that file creating and adding the tiles as you go.

Well, I'll need more objects, this is just the one I'm coding first. So how would I add the objects like you said? I don't understand the way you put it.

But the problem I see with this is how would I be able to add more tiles than just the same ground tile, like say a water tile or the player?

Alright, so what is the best way to get my scanner to read the file and write the variables to integers? Unless I'm missing something, I'd have to have a hardcoded maximum value of the X and Y position.

Like the 0th(or 1st) position of the row would be the object (example 1), then the next 4 would be the x position(example 0027), and finally the last 4 would be Y position(example 0001), with the full file reading "100270001". I really wouldn't like to do that, because a hardcoded maximum level size means more limitation, and I'd like the level format to be as non-limiting as possible (which is especially important since I want the game to eventually feature a level editor).

Please tell me if I'm wrong about this, as I hope I am.

The data on each line could be delimited (separated) by spaces instead of in fixed columns to allow for a larger range of numeric values.

Originally Posted by jps

I don't understand where you would have to define a maximum x and y.
if you place your integers in a text file with spaces between them you can easily get the next integer on the line no matter (within acceptable range for an integer) how large it is.
For example, a sample text file as follows:

4 lines with 5 integers each.

The reason I say I would have to set up a maximum X and Y is because of my read file method:

public void File(){
 
		try{
		l = new Scanner(new File("C://CWWLEVELS//world1stage1.txt"));
		while(l.hasNext()){
			for(int i=0; i < ((levelsizey)); i++){
				Level1.add(i,l.next());
			}
		}
		l.close();
		}catch(Exception e){
			System.out.println("error loading map");
		}

To read each integer I would assume I have to make different for loops to read each one like so:

public void File(){
 
		try{
		l = new Scanner(new File("C://CWWLEVELS//world1stage1.txt"));
		while(l.hasNext()){
			for(int i=0; i < ((levelsizey)); i++){
				Level1.add(i,l.next());
			}
for(int i=0; i < 1; i++){  //to read object id
				Level1.add(i,l.next());
}
or(int i=1; i < 5; i++){ //to read x and so on...
				Level1.add(i,l.next());
			}
		l.close();
		}catch(Exception e){
			System.out.println("error loading map");
		}

Once again, I hope I'm wrong...

If you want to read integer values you should use the nextInt() method. The next() method returns a String.

You should work on the logic needed to read in the data and use it in the program before trying to write the code. Your nested loops don't make sense to me. What is on each line being read in from the file?
What is to be done with each piece of data/number that is read in?
Define what is in each line in the file and then show how that should be read and used in the program.

Originally Posted by Norm

If you want to read integer values you should use the nextInt() method. The next() method returns a String.

You should work on the logic needed to read in the data and use it in the program before trying to write the code. Your nested loops don't make sense to me. What is on each line being read in from the file?
What is to be done with each piece of data/number that is read in?
Define what is in each line in the file and then show how that should be read and used in the program.

So I should change my code to something like this?:

public void File(){
 
		try{
		l = new Scanner(new File("C://CWWLEVELS//world1stage1.txt"));
		while(l.hasNext()){
			for(int i=0; i < ((levelsizey)); i++){
				Level1.add(i,l.nextInt());
			}
		}
		l.close();
		}catch(Exception e){
			System.out.println("error loading map");
		}

Correct, or is there something I'm missing?

Can you describe what is in the file being read and what you want to do with it when you read it into the program?

Currently the file has 3 integers per line in it like I was told, with spaces inbetween each. The first one is the item ID, when its a certain number, I want a certain object spawned (The main ground tile), the second one I want to be the X position of the object, and the third, the y position. Also, I haven't actually run the game since I've made these edits, as I want to make sure I correct the file reading method first (I know I'll get an error otherwise).

If a line has three items on it, you need to read the full line and separate it into the three parts so you can process each one as required.
The String split() method will separate the line into separate parts and put them into an array.
The Integer class's parseInt method will convert a String to an int value.

You should write a small test program that reads the file line by line, splits each line into its parts and prints out the parts to see how the methods work. When that works, you can merge the logic from the small test program into the larger program.

Okay, I'll modify my small array testing program and see if what you said works. Wish me luck!

Edit: Having a little trouble, am I reading the different parts of the array properly? (str1 is the array)

i1 = Integer.parseInt(str1[0]);
i2=Integer.parseInt(str1[1]);
i3=Integer.parseInt(str1[2]);

Sorry for the slight bump, but since the last post doesn't update for edits, I wanted to make sure people know that I've updated my post, hopefully reposting my question will make this post slightly less useless:

Am I reading from these arrays properly?

i1 = Integer.parseInt(str1[0]);
i2=Integer.parseInt(str1[1]);
i3=Integer.parseInt(str1[2]);

Thank you for your time.

Am I reading from these arrays properly?

What happens when you compile and execute the code? Does it work and do what you want?

When I try to run it, these are the errors that come up in eclipse:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
at stringtest.main.Main.readHeader(Main.java:70)
at stringtest.main.Main.<init>(Main.java:26)
at stringtest.main.Jframe.main(Jframe.java:15)

Since the other errors come up at the start of the "read" method, and when the Main object is added to the JFrame, it can't be either of them. If it helps, here's all the code:

package stringtest.main;
 
 
import java.awt.*;
import java.io.File;
import java.util.Scanner;
 
import javax.swing.JPanel;
 
 
public class Main extends JPanel{
 
	private String str1[] = new String [3];
	private Scanner lh;
	private String s1 = "13";
	private String s2 = "13";
	private String s3 = "0";
	private String s4 = "0";
	private int i1;
	private int i2;
	private int i3;
	private int i4;
 
public Main(){	
		openHeader();
		readHeader();
		closeHeader();
 
		i1 = Integer.parseInt(s1);
		i2=Integer.parseInt(s2);
		i3=Integer.parseInt(s3);
		i4=Integer.parseInt(s4);
	}
 
	public void paintComponent(Graphics g) {
    	super.paintComponent(g);
 
    	g.setColor(Color.BLACK);
    	g.drawString(s1,10,10);
    	g.drawString(s2,10,30);
    	g.drawString(s3,10,50);
    	g.drawString(s4,10,70);
 
    	if (i1==2 && i2==1 && i3==1){
    		g.drawString(s1,10,90);
        	g.drawString(s2,10,110);
        	g.drawString(s3,10,130);
        	g.drawString(s4,10,150);
    	}
 
	}
 
 
public void openHeader(){
 
		try{
		lh = new Scanner(new File("C://CWWLEVELS//world1stage1.txt"));
		}catch(Exception e){
			System.out.println("error loading configuration file");
		}
 
	}
 
	public void readHeader(){
 
	while(lh.hasNext()){
		for(int i=0; i < 1; i++){
			s1=lh.nextLine();
			str1=s1.split(s1);
			i1 = Integer.parseInt(str1[0]);
			i2=Integer.parseInt(str1[1]);
			i3=Integer.parseInt(str1[2]);
		}
	}
 
	}
 
	public void closeHeader(){
 
	lh.close();
 
	}
}