public interface Shape { 
 void draw(); 
} 

public class Rectangle implements Shape { 
 
 @Override 
 public void draw() { 
 System.out.println("Inside Rectangle::draw() method."); 
 } 
} 

public class Square implements Shape { 
 
 @Override 
 public void draw() { 
 System.out.println("Inside Square::draw() method."); 
 } 
} 

public class Circle implements Shape { 
 
 @Override 
 public void draw() { 
 System.out.println("Inside Circle::draw() method."); 
 } 
}

public class ShapeFactory { 
 
 //use getShape method to get object of type shape 
 public Shape getShape(String shapeType){ 
 if(shapeType == null){ 
 return null; 
 } 
 if(shapeType.equalsIgnoreCase("CIRCLE")){ 
 return new Circle(); 
 } else if(shapeType.equalsIgnoreCase("RECTANGLE")){ 
 return new Rectangle(); 
 } else if(shapeType.equalsIgnoreCase("SQUARE")){ 
 return new Square(); 
 } 
 return null; 
 } 
} 

public class FactoryPatternDemo { 
 
 public static void main(String[] args) { 
 ShapeFactory shapeFactory = new ShapeFactory(); 
 
 //get an object of Circle and call its draw method. 
 Shape shape1 = shapeFactory.getShape("CIRCLE"); 
 
 //call draw method of Circle 
 shape1.draw(); 
 
 //get an object of Rectangle and call its draw method. 
 Shape shape2 = shapeFactory.getShape("RECTANGLE"); 
 
 //call draw method of Rectangle 
 shape2.draw(); 
 
 //get an object of Square and call its draw method. 
 Shape shape3 = shapeFactory.getShape("SQUARE"); 
 
 //call draw method of circle 
 shape3.draw(); 
 } 
} 

Inside Circle::draw() method. 
Inside Rectangle::draw() method. 
Inside Square::draw() method. 

public class ThisEscape { 
... 
 public ThisEscape(EventSource source) { 
     source.registerListener(new EventListener() { 
                   public void onEvent(Event e) { 
                        doSomething(e); 
               } 
           }); 
 ... 
 } 
} 

public class SafeListener { 
     private final EventListener listener; 
     private SafeListener() { 
         listener = new EventListener() { 
                 public void onEvent(Event e) { 
                doSomething(e); 
          } 
         }; 
  } 

 public static SafeListener newInstance(EventSource source) { 
   SafeListener safe = new SafeListener(); 
   source.registerListener(safe.listener); 
 return safe; 
 } 
} 

Shape shape = shapeFactory.getShape("CIRCLE"); 

((Circle)shape).getRadius();

Shape getColorShape(String type , String color){ 
Shape shape = shapeFactory.getShape(type); 
shape.setColor(color);
return color; 
}

public Holder holder; 
 public void initialize() { 
    holder = new Holder(42); 
  } 
... 
  public class Holder { 
            private int n; 
 
     public Holder(int n) { 
        this.n = n; 
      } 

    public void assertSanity() { 
           if (n != n) 
            throw new AssertionError("This statement is false."); 
      } 
} 

//Thread1 
initialize(); 
 
//Thread2 
if (holder != null){ 
 holder.assertSanity(); 
}