Apex Code to Remove Lead Duplication | De-duping Leads in Salesforce

While working with the lead often we encounter the problem the data duplication and commonly lots of the free application are already hosted on the App-exchange addressing the issue of the duplicate records, the very common one and available for free

 Salesforce Lead Duplication

Yesterday I meat a requirement where I needed an Apex code to handle lead duplication and therefore I decide to move down writing some piece of code Apex code addressing the same issue. 

Below is the code to handle the lead duplication and can be used as base template to prevent duplication. Although this is base template lots of modification could be done in here to grow this to a better level