title: How to find duplicates in an ArrayList which is in the form of JSON object?
body: <p>I am having an option in my website for the user i.e: "Settings" in that I given 3 options(TextBoxes) to enter details: 1.E-mail, 2.SMS, 3.MMS.. in this user can enter another mail id: its an optional thing but, if he enter the both or same which is neccesary e-mail and optional or same then, I have to tell that "given e-mail" alredy exist. </p>
  
  <p>I am sending this data as ArrayList that to coverted as JSON object.</p>
  
  <p>What is the best way to find the duplicate and notify that to user</p>
  
  <p>Help me in this </p>
  
  <p>Thanks in advance</p>