Let's say it is a HashMap. Just store the HashMap as a single
serialiased object.

see http://mindprod.com/jgloss/serialization.html
http://mindprod.com/applets/fileio.html
to generate some sample code.

Try this program, it uses Generics feature compatible in JDK 5.0 or
above:

/*
*  WordReader.java - A program to read words from a file
*/
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

import java.util.List;
import java.util.ArrayList;

public class WordReader {
   public static void main( String[] args ) {
       // will store the words read from the file
       List<String> wordList = new ArrayList<String>();

       BufferedReader br = null;
       try {
           // attempt to open the words file
           br = new BufferedReader( new FileReader( "words.txt" ) );

           String word;

           // loop and read a line from the file as long as we dont
get null
           while( ( word = br.readLine() ) != null )
               // add the read word to the wordList
               wordList.add( word );
       } catch( IOException e ) {
           e.printStackTrace();
       } finally {
           try {
               // attempt the close the file
               br.close();
           } catch( IOException ex ) {
               ex.printStackTrace();
           }
       }

       // initialize a new string array equal to the size of the
wordList
       String[] words = new String[ wordList.size() ];

       // call the wordList's toArray method to and transfer items
from
       // wordList to our string array words
       wordList.toArray( words );

       // loop and display each word from the words array
       for( int i = 0; i < words.length; i++ )
           System.out.println( words[ i ] );
   }
}

Hope it helps!