Help with Designing a Simple Database

Question

I am currently working on a designing problem I would appreciate if someone could review my solution.
The Problem:
I need to create a simple database that contains the following entries�
First Name //mandatory
Last Name //mandatory
Date of Birth //mandatory
Hobbies //there could be anywhere from 0 to infinite amount of hobbies
Type of actions that I need to perform on the database�
Add, delete, and modify and entry
Below are a two design solutions I came up with�
For both solutions I am going to create two text files. One of the text files called profiles.txt will contain the following fields on each line�
Id, First Name, Last Name, Date of Birth
//the Id field in this text file will be the primary key so you will not see the Id duplicated
The other text file called hobbies.txt will contain the following fields on each line�
Id, hobby
//the Id field can be duplicated in this text file so a person can be linked to zero or several hobbies
Now what differs between my solutions is how I am going to read this data into my program�
Solution 1) When you start the program it will read the profiles.txt into a linked list. After that is finished the program will then load the hobbies into several linked list that the profiles linked list will point to. So basically each person will have a linked list of hobbies associated with him or her.
Problem I see with this solution is that if there were 200 million people contained in the profiles.txt would my program crash since the computer would not have enough memory to load all of those names?
Solution 2) Instead of loading the data at the start of the program the data will stay in the text files. So when someone does a search it will open the text file and search for the entry.
Problem with this solution is it would be hard to delete and modify names (would I have to rewrite the text file every time I do a change?). Would a good fix to this problem be creating a separate text file to keep track of any changes or deletions I do and once in a while do a database maintenance?
So a review of my questions is�
1)     Would my program crash if I had 200 million entries if I use my solution 1?
2)     Is my solution 2 possible without being incredibly slow or complicated?
3)     Is there another way of doing this I have not thought of?

Answer 1

I think having one option will do. Now the problem with this text file thing is that, we'll hve to read every information into memory if we are running a test driver for the program and then work on the information in memory.
After the program closes, whatever changes we made to this data in memory shd be written to file so we need to find a way of writing the data from memory to overwrite the file. I hope you kinda get what i'm talking abt.
the database will consist of information like this
String firstName
String lastName
String DOB
ArrayList / Vector Hobbies
Now, we kinda want to declare a class with with all these information as data fields ok.
so let's say
public class Try{
String firstName
String lastName
String DOB
ArrayList / Vector Hobbies
and then create an instance of this class in the driver
which will be an ArrayList of this class or something so each index of this class ArrayList will hve it's unique data information from the file we read in but again, this is kinda working in memory right.
After doing all we have to do, we want to write back to file all the changes we made to the data in memory. That's where we are kinda stuck right now.
A member of the group was suggesting we call whatever functions to work on the txt file which will mean we'll hve to re-write each time we call a function to operate on it and all that stuff. This is a slow process.
will be glad if anybody out there will have a better way to implement this. Thanks a lot.