Throws vs try catch

Question

We can use any one but which one is better to use and why ?

Answer 1

There is the school of thought that you should wrap some Exceptions in your own, so as to keep your classes independant.
The classic example is with a DAO (data access object)
Your DAO could use JDBC, or it could use flat file structure, or it could use HTTP to look up information. Which does it use? Who cares - as long as it gives you the info.
As such, a DAO should not throw any SQLException - because that reveals the inner workings of the DAO. Rather a custom exception - eg DAOException should be thrown that wraps the original exception, hiding the implementation details from the calling class.
So instead of your calling code catching SQLException, you catch DAOException.
// in DAO
public void saveUserRecord(User user) throws DAOException{
  Connection con = null;
  try{
    con = getConnection();
  catch(SQLException e){
    throw new DAOException("Error saving user", e);
  finally{
    try{  if (con != null) con.close(); }
    catch(SQLException e){}
// and in your user class
  try{
    dao.saveUserRecord(user);
  catch(DAOException e){
      logError("could not save user record");
      // do whatever else here.
   }