"Easy" Math.random() problem

[Darkone85]

Hey, im new to programming and studying at the university in Karlstad Sweden and have this assignment to make some blobs talk, wink, move and stuff.

I have these classes (and some more thats not important):

/**
 * Chapter 3: BlobApp.java
 * Our first interactive program.
 * Displays two "Blobs" that respond to mouse clicks.
 * @author Manne
 */
import wheels.users.*;

public class BlobApp extends Frame {
	private WinkingBlob _winkingBlob;
	private TalkativeBlob _talkativeBlob;
	private HappyBlob _happyBlob;
	private SadBlob _sadBlob;
	private ShyBlob _shyBlob;
	
	public BlobApp() {
		super();
		_winkingBlob = new WinkingBlob(300, 300);
		_talkativeBlob = new TalkativeBlob(400, 200, "I'm so happy!");
		_happyBlob = new HappyBlob(600, 400, "I'm always happy! ^^");
		_sadBlob = new SadBlob (100, 100, "I'm always sad :(");
		_shyBlob = new ShyBlob (200, 200);
	}
	
	public static void main(String [] args) {
		BlobApp app = new BlobApp();
	}
}

----------------

/**
 * Chapter 3: Blob.java
 * models a creature with two eyes.
 * @author Manne
 */

import wheels.users.*;

public class Blob extends Ellipse {
	protected Ellipse _leftEye, _rightEye;
	
	public Blob(int x, int y) {
		super(x, y);
		_leftEye = new Ellipse(java.awt.Color.black);
		_rightEye = new Ellipse(java.awt.Color.black);
		this.setSize(100, 100);
		_leftEye.setSize(30, 30);
		_rightEye.setSize(30, 30);
		_leftEye.setLocation(this.getLocation().x+22, this.getLocation().y+10);
		_rightEye.setLocation(this.getLocation().x+47, this.getLocation().y+10);
}
	
	public void mousePressed(java.awt.event.MouseEvent e) {
		this.setFillColor(java.awt.Color.blue);
	}
	
	public void mouseReleased(java.awt.event.MouseEvent e) {
		this.setFillColor(java.awt.Color.red);
	}
}

------------

/**
 * chapter 3: WinkingBlob.java
 * Extends the Blob class to add the ability to wink when clicked on.
 * @author Manne
 */

public class WinkingBlob extends Blob {
	public WinkingBlob(int x, int y) {
		super(x, y);
	}
	
	public void mousePressed(java.awt.event.MouseEvent e) {
		super.mousePressed(e);
		_rightEye.setSize(30, 5);
		_rightEye.setLocation(_rightEye.getLocation().x, _rightEye.getLocation().y+15);
	}
	
	public void mouseReleased(java.awt.event.MouseEvent e) {
		super.mouseReleased(e);
		_rightEye.setSize(30, 30);
		_rightEye.setLocation(_rightEye.getLocation().x, _rightEye.getLocation().y-15);
	}
}

---------

/**
 * Chapter 3: Modifying BlobApp-program and extends the Blob class so there's a new, 
 * "ShyBlob" who moves away when clicked on.
 * @author Manne
 */

public class ShyBlob extends Blob {
	public ShyBlob(int x, int y) {
		super(x, y);
	}
	
	public void mousePressed(java.awt.event.MouseEvent e) {
		//super.mousePressed(e);
	}
	
	public void mouseReleased(java.awt.event.MouseEvent e, ShyBlob _shyBlob) {
		//super.mouseReleased(e);
	}
}

--- NOW to the problem, how do I use Math.random() to say whenever I click shyblob he will disappear and appear on a new random x&y? I tried reading the API but it didnt tell me much.

Grateful for answers,
Manne

[Darkone85]

i could use:

this.setLocation(this.getLocation().x+50, this.getLocation().y+40); under the methods mousePressed/Released, but the thing is that they want us to use Math.random() and i dont know how to.

Tried to this.setLocation(Math.random()); but it wont work since it uses double

gaaaah!

[ZekeDragon]

public void mousePressed(java.awt.event.MouseEvent e)
{
    int[] nums = { (int) (Math.random() * (SCREEN_X - 50) + 50),
                   (int) (Math.random() * (SCREEN_Y - 50) + 50) };
    this.setLocation(nums[0], nums[1]);
}

That should work fine. Go ahead and give it a shot.

[Darkone85]

Well, it does work in one way and i think i understand it too. U create an vector with 2 elements which u cast from doubles to ints and says that setLocation= place [0] and [1] right..?

Only, since i need (?) to create local variables for screen_x and_y and initialize them to something the blob will always jump to those x&y and then just hop around 50x50 for each other click.

Maybe I can initialize them to = "between max and min" somehow?

[ZekeDragon]

Actually the reason I did all those maths was so there were 50 pixels from each border, so if the screen were, say, 800 x 600 pixels, it'd only select a region from 50 - 750 on the X coordinate and 50 - 550 on the Y coordinate. If you test it with those numbers set for SCREEN_X and SCREEN_Y, that's what will be returned. I chose 50 pixels because the blobs size is 100x100, but now that I think about it, the blobs location would be on the top left corner of the blob, not the center:

int[] nums = { (int) (Math.random() * (SCREEN_X - 100)),
               (int) (Math.random() * (SCREEN_Y - 100)) };

And the reason I made it an array like that was basically for Zero, One, Infinity. It'd be better to use a loop and DRY, but that'd require a little more writing and wasn't the point of the post.

[Darkone85]

I seeee! I just love it when I understand new concepts.

The thing i had problems was that to use math.random in the same line as this.setLocation - which is impossible? Only way you get around it, is like this, casting it to int instead? I tried with .floor and so on.

Well, thank you young Skywalker. Ill be back!