Thread: Help with method to check if two rectangles overlap

Hey everyone. I am working on a hw assignment where I have to create a class called Rectangle that is utilized in another program. The end result is a graphic of colored rectangles, which overlap in certain areas and change color where they overlap. I have to create a method called overlapWith that checks to see if two rectangles overlap.

if (redRect.overlapsWith(greenRect)) {
Rectangle overlap = redRect.getOverlap(greenRect);
overlap.draw(page);
This piece of code is from the program that utilizes the overlapsWith method I am trying to create. redRect and greenRect were rectangles that were previously defined. This is from my hw assignment: the overlapsWith method should return whether or not the rectangle you call it on (this) overlaps with another rectangle (the argument). Here's a strategy for checking if this rectangle overlaps with another:
If the left x of this rectangle is larger than the right x of the other (or vice versa), they don't overlap.
If the top y of this rectangle is larger than the bottom y of the other (or vice versa), they don't overlap.
Otherwise, they do overlap.
I am stuck and do not know how to start this method. How do I compare x,y data from two seperate variables? Any help would be appreciated.

Ok so I've got that last part finished. Now I need to create a getOverlap method that draws a new rectangle over the overlap, and assigns a new color that is the rgb value of both rectangles combined, but not to reach over 255 on any given value. I really don't know how to get this one started.

--- Update ---

// Jon Katz
// Initiates Rectangle class and draw and getOverlap methods.

import java.awt.Color;
import java.awt.Graphics;

public class Rectangle {

// Instance data for Rectangle class
private int x1;
private int y1;
private int x2;
private int y2;
private int r, g, b;


// Initialize instance data, Constructor
public Rectangle (int x1, int y1, int x2, int y2, int r, int g, int b) {

// Define variables
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
this.r = r;
this.g = g;
this.b = b;

}

// Create a draw method
public void draw(Graphics page) {

int width = x2 - x1;
int height = y2 - y1;
Color color = new Color (r, g, b);
page.setColor(color);
page.fillRect(x1, y1, width, height);
}

// Create overlapsWith method
public boolean overlapsWith(Rectangle a) {
return this.x2 >= a.x1 &&
this.x1 <= a.x2 &&
this.y2 >= a.y1 &&
this.y1 <= a.y2;
}
public void getOverlap(Rectangle a) {
r = this.r + a.r;
b = this.b + a.b;
g = this.g + a.g;
Color overlapColor = new Color (r, g, b);
page.setColor(overlapColor);
}

}

--- Update ---

// Lisa Torrey
// A custom panel that draws a pattern of overlapping rectangles.

import java.awt.*;
import javax.swing.*;

public class RectanglePanel extends JPanel {

public static final int WIDTH = 200; // Panel width
public static final int HEIGHT = 200; // Panel height
public static final int RGB_MAX = 255; // For colors

// Set the panel's size and color
public RectanglePanel() {
super.setPreferredSize(new Dimension(WIDTH, HEIGHT));
super.setBackground(Color.white);
}

// Draw some overlapping rectangles
public void paintComponent(Graphics page) {
super.paintComponent(page);

// A red one in the top left
Rectangle redRect = new Rectangle(0, 0, WIDTH/2, HEIGHT/2, RGB_MAX, 0, 0);
redRect.draw(page);

// A green one in the bottom right
Rectangle greenRect = new Rectangle(WIDTH/2, HEIGHT/2, WIDTH, HEIGHT, 0, RGB_MAX, 0);
greenRect.draw(page);

// A blue one in the middle
Rectangle blueRect = new Rectangle(WIDTH/4, HEIGHT/4, WIDTH*3/4, HEIGHT*3/4, 0, 0, RGB_MAX);
blueRect.draw(page);

// Possibly an overlap of red and green
if (redRect.overlapsWith(greenRect)) {
Rectangle overlap = redRect.getOverlap(greenRect);
overlap.draw(page);
}

// Possibly an overlap of red and blue
if (redRect.overlapsWith(blueRect)) {
Rectangle overlap = redRect.getOverlap(blueRect);
overlap.draw(page);
}

// Possibly an overlap of green and blue
if (greenRect.overlapsWith(blueRect)) {
Rectangle overlap = greenRect.getOverlap(blueRect);
overlap.draw(page);
}
}

// Create and display one of these panels
public static void main(String[] args) {

JFrame frame = new JFrame("Rectangle Panel");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS E);

RectanglePanel panel = new RectanglePanel();
frame.getContentPane().add(panel);

frame.pack();
frame.setVisible(true);
}
}

--- Update ---

The first is my code so far and the second is the test program. I am confused on how to set up the getOverlap method. Any ideas?

This thread has been cross posted here:

http://www.java-forums.org/new-java/70466-help-overlapping-rectangle-assignment.html

Although cross posting is allowed, for everyone's benefit, please read:

Java Programming Forums Cross Posting Rules

The Problems With Cross Posting