Java Design Patterns

com/javadevjournal/design/structural/decorator/Circle.java

@@ -0,0 +1,12 @@
+package javadevjournal.design.structural.decorator;
+
+/**
+ * @author Kunwar
+ */
+public class Circle implements Shape {
+
+	@Override
+	public void drawShape() {
+		System.out.println("The shape is: Circle");
+	}
+}

com/javadevjournal/design/structural/decorator/DecoratorPatternDemo.java

@@ -0,0 +1,29 @@
+package javadevjournal.design.structural.decorator;// DecoratorPatternDemo.java
+
+/**
+ * @author Kunwar
+ */
+public class DecoratorPatternDemo {
+
+	public static void main(String[] args) {
+		// Creating objects of Shape interface
+		Shape circle = new Circle();
+		Shape rectangle = new Rectangle();
+
+		// Creating objects of decorated classes
+		Shape redCircle = new RedShapeDecorator(new Circle());
+		Shape redRectangle = new RedShapeDecorator(new Rectangle());
+
+		System.out.println("Circle with normal fill");
+		circle.drawShape();
+
+		System.out.println("Rectangle with normal fill");
+		rectangle.drawShape();
+
+		System.out.println("\nCircle of red fill");
+		redCircle.drawShape();
+
+		System.out.println("\nRectangle of red fill");
+		redRectangle.drawShape();
+	}
+}

com/javadevjournal/design/structural/decorator/Rectangle.java

@@ -0,0 +1,12 @@
+package javadevjournal.design.structural.decorator;// Class 1
+
+/**
+ * @author Kunwar
+ */
+public class Rectangle implements Shape {
+
+	@Override
+	public void drawShape() {
+		System.out.println("The shape is: Rectangle");
+	}
+}

com/javadevjournal/design/structural/decorator/RedShapeDecorator.java

@@ -0,0 +1,27 @@
+package javadevjournal.design.structural.decorator;
+
+/**
+ * @author Kunwar
+ */
+public class RedShapeDecorator extends ShapeDecorator {
+
+	public RedShapeDecorator(Shape decoratedShape) {
+		super(decoratedShape);
+	}
+
+	@Override
+	public void drawShape() {
+		decoratedShape.drawShape();
+		//additional method to change the behavior of the shape object
+		shapeFill(decoratedShape);
+	}
+
+	/**
+	 * This method will change the behavior of the shape object at runtime.
+	 *
+	 * @param decoratedShape
+	 */
+	private void shapeFill(Shape decoratedShape) {
+		System.out.println("Shape Fill color: Red");
+	}
+}

com/javadevjournal/design/structural/decorator/Shape.java

@@ -0,0 +1,8 @@
+package javadevjournal.design.structural.decorator;
+
+/**
+ * @author Kunwar
+ */
+public interface Shape {
+	void drawShape();
+}

com/javadevjournal/design/structural/decorator/ShapeDecorator.java

@@ -0,0 +1,19 @@
+package javadevjournal.design.structural.decorator;
+
+/**
+ * @author Kunwar
+ */
+public abstract class ShapeDecorator implements Shape {
+
+	//protected object of Shape Interface.
+	protected Shape decoratedShape;
+
+	public ShapeDecorator(Shape decoratedShape) {
+		this.decoratedShape = decoratedShape;
+	}
+
+	//calling the drawShape method on decoratedShape
+	public void drawShape() {
+		decoratedShape.drawShape();
+	}
+}