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Author: divScorp

designPattern/Decorator/DecorateIcecream.java

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+package designPattern.Decorator;
+
+public abstract class DecorateIcecream implements Icecream {
+	Icecream icecream;
+}
+
+class Chocolate extends DecorateIcecream{
+	public Chocolate(Icecream icecream) {
+		this.icecream = icecream;
+	}
+
+	@Override
+	public String description() {
+		return "Chocolate";
+	}
+
+	@Override
+	public Double cost() {
+		return this.icecream.cost() + 5.0;
+	}
+}
+
+class Peanuts extends DecorateIcecream{
+	public Peanuts(Icecream icecream) {
+		this.icecream = icecream;
+	}
+
+	@Override
+	public String description() {
+		return "Peanuts";
+	}
+
+	@Override
+	public Double cost() {
+		return this.icecream.cost() + 3.0;
+	}
+}

designPattern/Decorator/Icecream.java

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+package designPattern.Decorator;
+
+public interface Icecream {
+	public String description();
+
+	public Double cost();
+}
+
+class Vanilla implements Icecream {
+
+	@Override
+	public String description() {
+		return "Vanila Icecream!";
+	}
+
+	@Override
+	public Double cost() {
+		return 15.0;
+	}
+}
+
+class Strawberry implements Icecream {
+
+	@Override
+	public String description() {
+		return "Strawberry Icecream!";
+	}
+
+	@Override
+	public Double cost() {
+		return 20.0;
+	}
+}

designPattern/Decorator/TestDecorator.java

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+package designPattern.Decorator;
+
+public class TestDecorator {
+
+	public static void main(String[] args) {
+		Icecream vanilla = new Vanilla();
+		System.out.println("Simple vanilla cost: " + vanilla.cost());
+		
+		Icecream vanillaWithPeanuts = new Peanuts(vanilla);
+		System.out.println("Vanilla with peanuts cost: " + vanillaWithPeanuts.cost());
+		
+		Icecream vanillaWithChocolate = new Chocolate(vanilla);
+		System.out.println("Vanilla with chocolate cost: " + vanillaWithChocolate.cost());
+
+	}
+
+}

designPattern/Observer/Observer.java

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+package designPattern.Observer;
+
+public interface Observer {
+	public void update(String message);
+	public void display();
+}

designPattern/Observer/Student.java

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+package designPattern.Observer;
+
+public class Student implements Observer{
+
+	private String message;
+	public Student(StudentData data) {
+		data.registerObserver(this);
+	}
+	
+	public void update(String message) {
+		this.message = message;
+		display();
+	}
+	public void display() {
+		System.out.println(this.message);
+	}
+}

designPattern/Observer/StudentData.java

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+package designPattern.Observer;
+
+import java.util.ArrayList;
+
+public class StudentData {
+		private String message;
+		private ArrayList<Observer> observers;
+		
+		public StudentData() {
+			observers = new ArrayList<>();
+		}	
+		public void registerObserver(Observer o) {
+			observers.add(o);
+		}
+		public void removeObserver(Observer o) {
+			observers.remove(o);
+		}
+		
+		public void notifyObservers() {
+			for(int i = 0; i < observers.size(); i++) {
+				Observer obs = (Observer) observers.get(i);
+				obs.update(message);
+			}
+		}
+		
+		public void setMessage(String msg) {
+			this.message = msg;
+		}
+		
+		public String getMessage() {
+			return this.message;
+		}
+}

designPattern/Observer/TestObserver.java

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+package designPattern.Observer;
+
+public class TestObserver {
+
+	public static void main(String[] args) {
+		StudentData data = new StudentData();
+		Observer std = new Student(data);
+		String msg = "Hello World";
+		data.setMessage(msg);
+		
+		if(!data.getMessage().equals("")) {
+			data.notifyObservers();
+		}
+		
+		data.removeObserver(std);
+		if(!data.getMessage().equals("")) {
+			data.notifyObservers();
+		}
+
+	}
+
+}

designPattern/Singleton/Settings.java

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+package designPattern.Singleton;
+
+public class Settings {
+	private static Settings firstObject = null;
+	private String font = "calibri";
+	private String color = "black";
+
+	private Settings() {
+	}
+
+	public static Settings getObject() {
+		if (firstObject == null) {
+			firstObject = new Settings();
+		}
+		return firstObject;
+	}
+
+	public void setFont(String fontName) {
+		this.font = fontName;
+	}
+
+	public void setColor(String colorName) {
+		this.color = colorName;
+	}
+
+	public String getFont() {
+		return this.font;
+	}
+
+	public String getColor() {
+		return this.color;
+	}
+}

designPattern/Singleton/TestSetting.java

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+package designPattern.Singleton;
+
+public class TestSetting {
+
+	public static void main(String[] args) {
+		Settings setting = Settings.getObject();
+		System.out.println("Setting Object Color: " + setting.getColor());
+		System.out.println("Font: " + setting.getFont());
+		Settings set1=Settings.getObject();
+		set1.setColor("Red");
+		System.out.println("Set Object Color: " + set1.getColor());
+		System.out.println("Font: " + set1.getFont());
+		System.out.println("Setting Object Color: " + setting.getColor());
+	}
+}