A simple telephone number database that uses a property list.

Here is a Java Program to A simple telephone number database that uses a property list.

import java.io.*;
import java.util.*;

class Phonebook {
  public static void main(String args[]) 
    throws IOException
  {
    Properties ht = new Properties();
    BufferedReader br =
      new BufferedReader(new InputStreamReader(System.in));
    String name, number;
    FileInputStream fin = null;
    boolean changed = false;

    // Try to open phonebook.dat file.
    try {
      fin = new FileInputStream("phonebook.dat");
    } catch(FileNotFoundException e) {
      // ignore missing file
    }

    /* If phonebook file already exists, 
       load existing telephone numbers. */
    try {
      if(fin != null) {
        ht.load(fin);
        fin.close();
      }
    } catch(IOException e) {
      System.out.println("Error reading file.");
    }

    // Let user enter new names and numbers.
    do {
      System.out.println("Enter new name" + 
                         " ('quit' to stop): ");
      name = br.readLine();
      if(name.equals("quit")) continue;

      System.out.println("Enter number: ");
      number = br.readLine();

      ht.put(name, number);
      changed = true;
    } while(!name.equals("quit"));

    // If phone book data has changed, save it.
    if(changed) {
      FileOutputStream fout = new FileOutputStream("phonebook.dat");

      ht.store(fout, "Telephone Book");    
      fout.close();
    }

    // Look up numbers given a name.
    do {
      System.out.println("Enter name to find" +
                         " ('quit' to quit): ");
      name = br.readLine();
      if(name.equals("quit")) continue;

      number = (String) ht.get(name);
      System.out.println(number);
    } while(!name.equals("quit"));
  }
}

Output of Above Java Program
sanjay
Enter number:
9977777516
Enter new name ('quit' to stop):
Hell
Enter number:
442312345348
Enter new name ('quit' to stop):
ASDF
Enter number:
4647511366489
Enter new name ('quit' to stop):
quit
Enter name to find ('quit' to quit):
sanjay
9977777516
Enter name to find ('quit' to quit):
asdf
null
Enter name to find ('quit' to quit):
ASDF
4647511366489
Enter name to find ('quit' to quit):
quit