public static boolean userExists(String userName) {
		 if(conn == null)
			 getConnection();
		 
		 boolean userFound = false;
		 
		 PreparedStatement stmt = null;
		 ResultSet rs = null;
		 try {
			 stmt = conn.prepareStatement("Select * from usuarios WHERE username = ?");
			 
			 stmt.setString(1, userName);
			 
			 rs = stmt.executeQuery();
			 
			 if(rs != null) {
			 
				  if ( rs.next() ) {
					  userFound = true;
				  }
				  
				  rs.close();
				 }
		 }
		 catch (SQLException e) {
			 e.printStackTrace();
		 }
	      
		 finally {
			 if(stmt != null) {
				try {
					stmt.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			 }
			 if(rs != null) {
					try {
						rs.close();
					} catch (SQLException e) {
						e.printStackTrace();
					}
			 }
		 }
		 
		 return userFound;
	 }