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JAVA
DESIGN PATTERNS
Creational
Patterns - Prototype Pattern
The
prototype means making a clone. This implies
cloning of an object to avoid creation. If the
cost of creating a new object is large and creation
is resource intensive, we clone the object.
We use the interface Cloneable and call its
method clone() to clone the object.
Again
let’s try and understand this with the help
of a non-software example. I am stressing on
general examples throughout this write-up because
I find them easy to understand and easy to accept
as we all read and see them in day-to-day activity.
The example here we will take will be of a plant
cell. This example is a bit different from the
actual cloning in a way that cloning involves
making a copy of the original one. Here, we
break the cell in two and make two copies and
the original one does not exist. But, this example
will serve the purpose. Let’s say the Mitotic
Cell Division in plant cells.
Let’s take a class PlantCell having a method
split(). The plant cell will implement the interface
Cloneable.
Following
is the sample code for class PlantCell.
PlantCell.java
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package creational.builder;
/**
* Shows the Mitotic cell division in the
plant cell.
*/
public class PlantCell implements Cloneable
{
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public
Object split() { |
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try
{ |
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return
super.clone();
}catch(Exception e) {
System.out.println("Exception occured:
"+e.getMessage());
return null;
} |
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} |
| }//
End of class |
Now
let’s see, how this split method works for PlantCell
class. We will make another class CellDivision
and access this method.
CellDivision.java
package
creational.prototype;
/**
* Shows how to use the clone.
*/
public class CellDivision {
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public static void main(String[] args) {
PlantCell cell = new PlantCell();
// create a clone
PlantCell newPlantCell = (PlantCell)cell.split();
}
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| }//
End of class |
One thing is you cannot use the clone as it is.
You need to instantiate the clone before using
it. This can be a performance drawback. This also
gives sufficient access to the data and methods
of the class. This means the data access methods
have to be added to the prototype once it has
been cloned.
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