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java flyweight design pattern


Java flyweight design pattern comes under structural design patterns and it is used to reduce number of object creation by reusing the existing similar objects. Only create a new object if there is no matching object.

Main advantage of flyweight design pattern is that, it reduces memory consumption by controlling the amount object creation.

Let’s discuss flyweight design pattern by below example. We are going to create 10 Rectangle with different colors but will restrict the object creation. Max 3 objects will be created.

Example

Shape.java

package com.codesjava;
 
public interface Shape {
	public void createShape();
}

Rectangle.java

package com.codesjava;
 
public class Rectangle implements Shape {
	private String color;
	private int length;
	private int width;
 
	public Rectangle(String color){
		this.color = color;		
	}
 
	@Override
	public void createShape() {
		 System.out.println("Rectangle created with following properties:");
		 System.out.println("Color: " + color);
		 System.out.println("Length: " + length);
		 System.out.println("Width: " + width);
	}
 
	public int getLength() {
		return length;
	}
 
	public void setLength(int length) {
		this.length = length;
	}
 
	public int getWidth() {
		return width;
	}
 
	public void setWidth(int width) {
		this.width = width;
	}
 
}

ShapeFactory.java

package com.codesjava;
 
import java.util.HashMap;
 
public class ShapeFactory {
	private static final HashMap<String, Rectangle> rectangleMap = new HashMap<String, Rectangle>();
 
	public static Shape getCircle(String color) {
	      Rectangle rectangle = (Rectangle)rectangleMap.get(color);
 
	      if(rectangle == null) {
	    	  rectangle = new Rectangle(color);
	         rectangleMap.put(color, rectangle);
	         System.out.println("Creating circle of color : " + color);
	      }
	      return rectangle;
	}
}

FlyweightPatternTest.java

package com.codesjava;
 
public class FlyweightPatternTest {
   private static final String colors[] = { "Red", "Green", "Blue"};
   private static String getRandomColor() {
      return colors[(int)(Math.random()*colors.length)];
   }
   private static int getRandomLength() {
      return (int)(Math.random()*100 );
   }
   private static int getRandomWeight() {
      return (int)(Math.random()*100);
   }  
   public static void main(String args[]){	   
	   for(int i=0; i < 10; ++i) {
	         Rectangle rectangle = (Rectangle)ShapeFactory.getCircle(getRandomColor());
	         rectangle.setLength(getRandomLength());
	         rectangle.setWidth(getRandomWeight());
	         rectangle.createShape();
	      }
	   }
}

Output

Creating circle of color : Blue
Rectangle created with following properties:
Color: Blue
Length: 0
Width: 43
Creating circle of color : Red
Rectangle created with following properties:
Color: Red
Length: 6
Width: 9
Creating circle of color : Green
Rectangle created with following properties:
Color: Green
Length: 24
Width: 24
Rectangle created with following properties:
Color: Green
Length: 68
Width: 26
Rectangle created with following properties:
Color: Blue
Length: 54
Width: 34
Rectangle created with following properties:
Color: Green
Length: 92
Width: 58
Rectangle created with following properties:
Color: Blue
Length: 12
Width: 31
Rectangle created with following properties:
Color: Blue
Length: 56
Width: 0
Rectangle created with following properties:
Color: Blue
Length: 43
Width: 27
Rectangle created with following properties:
Color: Blue
Length: 40
Width: 80


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