Composite is a structural design pattern that allows composing objects into a tree-like structure and work with the it as if it was a singular object.
Composite became a pretty popular solution for the most problems that require building a tree structure. Composite’s great feature is the ability to run methods recursively over the whole tree structure and sum up the results.
We will be using the java.awt library in our demo. Let's create a package first. The name of the package will be shapes. Inside of this package we place the *interface* Shape.
import java.awt.*;
public interface Shape {
int getX();
int getY();
int getWidth();
int getHeight();
void move(int x, int y);
boolean isInsideBounds(int x, int y);
void select();
void unSelect();
boolean isSelected();
void paint(Graphics graphics);
}
Let's also create a base class we call BaseShape and it will implement Shape.
import java.awt.*;
abstract class BaseShape implements Shape {
public int x;
public int y;
public Color color;
private boolean selected = false;
BaseShape(int x, int y, Color color) {
this.x = x;
this.y = y;
this.color = color;
}
@Override
public int getX() {
return x;
}
@Override
public int getY() {
return y;
}
@Override
public int getWidth() {
return 0;
}
@Override
public int getHeight() {
return 0;
}
@Override
public void move(int x, int y) {
this.x += x;
this.y += y;
}
@Override
public boolean isInsideBounds(int x, int y) {
return x > getX() && x < (getX() + getWidth()) &&
y > getY() && y < (getY() + getHeight());
}
@Override
public void select() {
selected = true;
}
@Override
public void unSelect() {
selected = false;
}
@Override
public boolean isSelected() {
return selected;
}
void enableSelectionStyle(Graphics graphics) {
graphics.setColor(Color.LIGHT_GRAY);
Graphics2D g2 = (Graphics2D) graphics;
float dash1[] = {2.0f};
g2.setStroke(new BasicStroke(1.0f,
BasicStroke.CAP_BUTT,
BasicStroke.JOIN_MITER,
2.0f, dash1, 0.0f));
}
void disableSelectionStyle(Graphics graphics) {
graphics.setColor(color);
Graphics2D g2 = (Graphics2D) graphics;
g2.setStroke(new BasicStroke());
}
@Override
public void paint(Graphics graphics) {
if (isSelected()) {
enableSelectionStyle(graphics);
}
else {
disableSelectionStyle(graphics);
}
// ...
}
}
Let's create a Dot class.
We will also put it in the *shapes* **package**.
import java.awt.*;
public class Dot extends BaseShape {
private final int DOT_SIZE = 3;
public Dot(int x, int y, Color color) {
super(x, y, color);
}
@Override
public int getWidth() {
return DOT_SIZE;
}
@Override
public int getHeight() {
return DOT_SIZE;
}
@Override
public void paint(Graphics graphics) {
super.paint(graphics);
graphics.fillRect(x - 1, y - 1, getWidth(), getHeight());
}
}
Let's also add a Circle to our shapes package.
import java.awt.*;
public class Circle extends BaseShape {
public int radius;
public Circle(int x, int y, int radius, Color color) {
super(x, y, color);
this.radius = radius;
}
@Override
public int getWidth() {
return radius * 2;
}
@Override
public int getHeight() {
return radius * 2;
}
public void paint(Graphics graphics) {
super.paint(graphics);
graphics.drawOval(x, y, getWidth() - 1, getHeight() - 1);
}
}
Let's also create a Rectangle shape class.
import java.awt.*;
public class Rectangle extends BaseShape {
public int width;
public int height;
public Rectangle(int x, int y, int width, int height, Color color) {
super(x, y, color);
this.width = width;
this.height = height;
}
@Override
public int getWidth() {
return width;
}
@Override
public int getHeight() {
return height;
}
@Override
public void paint(Graphics graphics) {
super.paint(graphics);
graphics.drawRect(x, y, getWidth() - 1, getHeight() - 1);
}
}
```
Lastly we'll create a CompoundShape class that will be extended with the BaseShape class.
import java.awt.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class CompoundShape extends BaseShape {
protected List <TheRayCode.composite.shapes.Shape> children = new ArrayList<>();
public CompoundShape(TheRayCode.composite.shapes.Shape... components) {
super(0, 0, Color.BLACK);
add(components);
}
public void add(TheRayCode.composite.shapes.Shape component) {
children.add(component);
}
public void add(TheRayCode.composite.shapes.Shape... components) {
children.addAll(Arrays.asList(components));
}
public void remove(TheRayCode.composite.shapes.Shape child) {
children.remove(child);
}
public void remove(TheRayCode.composite.shapes.Shape... components) {
children.removeAll(Arrays.asList(components));
}
public void clear() {
children.clear();
}
@Override
public int getX() {
if (children.size() == 0) {
return 0;
}
int x = children.get(0).getX();
for (TheRayCode.composite.shapes.Shape child : children) {
if (child.getX() < x) {
x = child.getX();
}
}
return x;
}
@Override
public int getY() {
if (children.size() == 0) {
return 0;
}
int y = children.get(0).getY();
for (TheRayCode.composite.shapes.Shape child : children) {
if (child.getY() < y) {
y = child.getY();
}
}
return y;
}
@Override
public int getWidth() {
int maxWidth = 0;
int x = getX();
for (TheRayCode.composite.shapes.Shape child : children) {
int childsRelativeX = child.getX() - x;
int childWidth = childsRelativeX + child.getWidth();
if (childWidth > maxWidth) {
maxWidth = childWidth;
}
}
return maxWidth;
}
@Override
public int getHeight() {
int maxHeight = 0;
int y = getY();
for (TheRayCode.composite.shapes.Shape child : children) {
int childsRelativeY = child.getY() - y;
int childHeight = childsRelativeY + child.getHeight();
if (childHeight > maxHeight) {
maxHeight = childHeight;
}
}
return maxHeight;
}
@Override
public void move(int x, int y) {
for (TheRayCode.composite.shapes.Shape child : children) {
child.move(x, y);
}
}
@Override
public boolean isInsideBounds(int x, int y) {
for (TheRayCode.composite.shapes.Shape child : children) {
if (child.isInsideBounds(x, y)) {
return true;
}
}
return false;
}
@Override
public void unSelect() {
super.unSelect();
for (TheRayCode.composite.shapes.Shape child : children) {
child.unSelect();
}
}
public boolean selectChildAt(int x, int y) {
for (Shape child : children) {
if (child.isInsideBounds(x, y)) {
child.select();
return true;
}
}
return false;
}
@Override
public void paint(Graphics graphics) {
if (isSelected()) {
enableSelectionStyle(graphics);
graphics.drawRect(getX() - 1, getY() - 1, getWidth() + 1, getHeight() + 1);
disableSelectionStyle(graphics);
}
for (TheRayCode.composite.shapes.Shape child : children) {
child.paint(graphics);
}
}
}
Let's create an editor package and place in it the ImageEditor class.
import TheRayCode.composite.shapes.CompoundShape;
import TheRayCode.composite.shapes.Shape;
import javax.swing.*;
import javax.swing.border.Border;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
public class ImageEditor {
private EditorCanvas canvas;
private CompoundShape allShapes = new CompoundShape();
public ImageEditor() {
canvas = new EditorCanvas();
}
public void loadShapes(Shape... shapes) {
allShapes.clear();
allShapes.add(shapes);
canvas.refresh();
}
private class EditorCanvas extends Canvas {
JFrame frame;
private static final int PADDING = 10;
EditorCanvas() {
createFrame();
refresh();
addMouseListener(new MouseAdapter() {
@Override
public void mousePressed(MouseEvent e) {
allShapes.unSelect();
allShapes.selectChildAt(e.getX(), e.getY());
e.getComponent().repaint();
}
});
}
void createFrame() {
frame = new JFrame();
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
JPanel contentPanel = new JPanel();
Border padding = BorderFactory.createEmptyBorder(PADDING, PADDING, PADDING, PADDING);
contentPanel.setBorder(padding);
frame.setContentPane(contentPanel);
frame.add(this);
frame.setVisible(true);
frame.getContentPane().setBackground(Color.LIGHT_GRAY);
}
public int getWidth() {
return allShapes.getX() + allShapes.getWidth() + PADDING;
}
public int getHeight() {
return allShapes.getY() + allShapes.getHeight() + PADDING;
}
void refresh() {
this.setSize(getWidth(), getHeight());
frame.pack();
}
public void paint(Graphics graphics) {
allShapes.paint(graphics);
}
}
}
Now we create a Demo class.
import TheRayCode.composite.editor.ImageEditor;
import TheRayCode.composite.shapes.Circle;
import TheRayCode.composite.shapes.CompoundShape;
import TheRayCode.composite.shapes.Dot;
import TheRayCode.composite.shapes.Rectangle;
import java.awt.*;
public class Demo {
public static void main(String[] args) {
System.out.println("The Ray Code is AWESOME!!!");
ImageEditor editor = new ImageEditor();
editor.loadShapes(
new Circle(10, 10, 10, Color.BLUE),
new CompoundShape(
new Circle(110, 110, 50, Color.RED),
new Dot(160, 160, Color.RED)
),
new CompoundShape(
new Rectangle(250, 250, 100, 100, Color.GREEN),
new Dot(240, 240, Color.GREEN),
new Dot(240, 360, Color.GREEN),
new Dot(360, 360, Color.GREEN),
new Dot(360, 240, Color.GREEN)
)
);
}
}
Let's compile and run.
We should get:
The Ray Code is AWESOME!!!
The Ray Code is AWESOME!!!
wikipedia
Find Ray on:
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The Ray Code
Ray Andrade
