Example of Bag Data Structure

Shell Script to copy files in Unix and checking for Locked files.

Abstract Factory & Factory Method Pattern

Factory Method Design Pattern

Portfolio Selection

Template Methods Design Pattern .. With object Injection using generics.

Hinernate Lazy Load vs Select Statements.

Select statements are very expensive in Hibernate as discussed in my last post on Hibernate Performance. Therefore, the best alternative to avoid selects statements is not to use Lazy loading. Lazy loading does not come without a price, lazy loading is very memory intensive operation and should be used with extensive care.

Template Method Design Pattern

abstract class Fruit {
  
    // Is the implementation of a template method which will be used in all the subclasses.
    // This pattern is implemented by a Implementation Inheritance.
    public final void eat(){
        System.out.println("I am eating :" + this.getClass().getName());
    }
  
    abstract void cut();
}

class Apple extends Fruit{

    @Override
    void cut() {
        System.out.println("This is how we cut : " + this.getClass().getName());
    }
  
}

class Banana extends Fruit{

    @Override
    void cut() {
        System.out.println("This is how we cut : " + this.getClass().getName());
    }
  
}

public class TemplateMethodPattern {
    public static void main(String args[]){
        Fruit apple = new Apple();
        apple.eat();
        apple.cut();
        Fruit banana = new Banana();
        banana.eat();
        banana.cut();
    }
}

Common Software Design Patterns

Gang of Four Design Patterns

HQL with Spring JDBC

After doing some more research the following is my suggestion to improve
performance. I am not sure how easily it's possible, if its' really
possible.

I would recommend using "HQL with Spring JDBC".

Spring JDBC basically makes using JDBC easier but still uses JDBC, so we
can get good performance.

HQL helps us write standard queries which mean we can get cross platform
flexibility as well.

What do you think? Is this combination possible?

Hibernate Performance.

After reading a few posts on the internet the following are my
conclusions:

1. Insert or Update operations in Hibernate work fairly good (not as
good as JDBC but close). So we do not need to do any improvement around
those operations other than just doing inserts in batch and avoid
Updates as they are costly anyways.

2. Select operation is very costly in Hibernate as compared JDBC. The
reason is hibernation of Data in objects. We can not avoid selects and
the way we program in hibernate we do a lot of them. The only way around
this problem is caching. We need to attach hibernate with a cache or
enable it if its already present in Hibernate.

3. Another improvement is to use Opportunistic locking by marking our
selects transactions as read-only.

So, basically Hibernate has an overhead and so will spring. Ease of
programming comes with a cost, now the question is how to reduce the
performance cost and keep achieving our Benchmark targets.