OOD

// Open-Close Principle - Bad example
 class GraphicEditor {
 
 	public void drawShape(Shape s) {
 		if (s.m_type==1)
 			drawRectangle(s);
 		else if (s.m_type==2)
 			drawCircle(s);
 	}
 	public void drawCircle(Circle r) {....}
 	public void drawRectangle(Rectangle r) {....}
 }
 
 class Shape {
 	int m_type;
 }
 
 class Rectangle extends Shape {
 	Rectangle() {
 		super.m_type=1;
 	}
 }
 
 class Circle extends Shape {
 	Circle() {
 		super.m_type=2;
 	}
 } 

// Violation of Likov's Substitution Principle
class Rectangle
{
	protected int m_width;
	protected int m_height;
	public void setWidth(int width){
		m_width = width;
	}
	public void setHeight(int height){
		m_height = height;
	}
	public int getWidth(){
		return m_width;
	}
	public int getHeight(){
		return m_height;
	}
	public int getArea(){
		return m_width * m_height;
	}	
}
class Square extends Rectangle 
{
	public void setWidth(int width){
		m_width = width;
		m_height = width;
	}
	public void setHeight(int height){
		m_width = height;
		m_height = height;
	}
}
class LspTest
{
	private static Rectangle getNewRectangle()
	{
		// it can be an object returned by some factory ... 
		return new Square();
	}
	public static void main (String args[])
	{
		Rectangle r = LspTest.getNewRectangle();
        
		r.setWidth(5);
		r.setHeight(10);
		// user knows that r it's a rectangle. 
		// It assumes that he's able to set the width and height as for the base class
		System.out.println(r.getArea());
		// now he's surprised to see that the area is 100 instead of 50.
	}
}

/
  / Dependency Inversion Principle - Good example
interface IWorker {
	public void work();
}
class Worker implements IWorker{
	public void work() {
		// ....working
	}
}
class SuperWorker  implements IWorker{
	public void work() {
		//.... working much more
	}
}
class Manager {
	IWorker worker;
	public void setWorker(IWorker w) {
		worker = w;
	}
	public void manage() {
		worker.work();
	}
}

// single responsibility principle - good example
interface IEmail {
	public void setSender(String sender);
	public void setReceiver(String receiver);
	public void setContent(IContent content);
}
interface Content {
	public String getAsString(); // used for serialization
}
class Email implements IEmail {
	public void setSender(String sender) {// set sender; }
	public void setReceiver(String receiver) {// set receiver; }
	public void setContent(IContent content) {// set content; }
}

// interface segregation principle - good example
interface IWorker extends Feedable, Workable {
}
interface IWorkable {
	public void work();
}
interface IFeedable{
	public void eat();
}
class Worker implements IWorkable, IFeedable{
	public void work() {
		// ....working
	}
	public void eat() {
		//.... eating in launch break
	}
}
class Robot implements IWorkable{
	public void work() {
		// ....working
	}
}
class SuperWorker implements IWorkable, IFeedable{
	public void work() {
		//.... working much more
	}
	public void eat() {
		//.... eating in launch break
	}
}
class Manager {
	Workable worker;
	public void setWorker(Workable w) {
		worker=w;
	}
	public void manage() {
		worker.work();
	}
}