Question

Write a program in Java using netbeans IDE that stores, retrieves, adds, and updates addresses as shown in figure 17.20. Use a fixed length string for storing each attribute in the address. Use random access file for reading and writing an address. Assume that the size of name, street, city, state, and zip is 32, 32,20, 2, 5 chars, respectively.

Answer 1

Java program to retrieve,add,update the addresses from the file.

Here there are two Java Classes. 1) Address.java 2) CreateAddressFile.java

Copy these classes to your editor and execute CreateAddressFile.java

Address.java : Class to hold the address properites and functions to write and read from the File.

import java.io.IOException;

import java.io.RandomAccessFile;

class Address {

private String name;

private String street;

private String city;

private String state;

private String zip;

// function to read the random access file and set the address properties.

void read(RandomAccessFile raf) throws IOException {

char[] temp = new char[32];

for (int i = 0; i < temp.length; i++)

temp[i] = raf.readChar();

name = new String(temp);

temp = new char[32];

for (int i = 0; i < temp.length; i++)

temp[i] = raf.readChar();

street = new String(temp);

temp = new char[20];

for (int i = 0; i < temp.length; i++)

temp[i] = raf.readChar();

city = new String(temp);

temp = new char[2];

for (int i = 0; i < temp.length; i++)

temp[i] = raf.readChar();

state = new String(temp);

temp = new char[5];

for (int i = 0; i < temp.length; i++)

temp[i] = raf.readChar();

zip = new String(temp);

}

//function to read the properties and add to the random access file.

void write(RandomAccessFile raf) throws IOException {

StringBuffer sb;

if (name != null)

sb = new StringBuffer(name);

else

sb = new StringBuffer();

sb.setLength(32);

raf.writeChars(sb.toString());

if (street != null)

sb = new StringBuffer(street);

else

sb = new StringBuffer();

sb.setLength(32);

raf.writeChars(sb.toString());

if (city != null)

sb = new StringBuffer(city);

else

sb = new StringBuffer();

sb.setLength(20);

raf.writeChars(sb.toString());

if (state != null)

sb = new StringBuffer(state);

else

sb = new StringBuffer();

sb.setLength(2);

raf.writeChars(sb.toString());

if (zip != null)

sb = new StringBuffer(zip);

else

sb = new StringBuffer();

sb.setLength(5);

raf.writeChars(sb.toString());

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getStreet() {

return street;

}

public void setStreet(String street) {

this.street = street;

}

public String getCity() {

return city;

}

public void setCity(String city) {

this.city = city;

}

public String getState() {

return state;

}

public void setState(String state) {

this.state = state;

}

public String getZip() {

return zip;

}

public void setZip(String zip) {

this.zip = zip;

}

//fucntion to find the size of the file based on the records length.

int size() {

return 2 * (32 + 32 + 20 + 2+ 5);

}

}

======================================================================================

2) CreateAddressFile.java : Class that holds Address data and do create/retrieval/update operations on it in the RandomAccessFile.

/*

* Java Program to Create/Update and Read the Address using RandomAccess File.

*/

import java.io.RandomAccessFile;

public class CreateAddressFile {

public static void main(String[] args) throws Exception {

// Sample data to store 3 address into the file.  

String[] names = { "A", "B", "C" };

String[] streets = { "abc", "def", "xyz" };

String[] cities = { "Boston", "Newyork", "Seatle" };

String[] states = { "LA", "CA", "NY" };

String[] zips = { "12345", "67891", "23456" };

// opening the file address.dat in read/write mode to store addresses.

RandomAccessFile raf = new RandomAccessFile("address.dat", "rw");

Address address = new Address();

for (int i = 0; i < names.length; i++) {

address.setName(names[i]);

address.setStreet(streets[i]);

address.setCity(cities[i]);

address.setState(states[i]);

address.setZip(zips[i]);

address.write(raf);

}

// opening the created file address.dat to read and display the content.

raf = new RandomAccessFile("address.dat", "rw");

address = new Address();

int numRecords = names.length;

for (int i = 0; i < numRecords; i++) {

address.read(raf);

System.out.print(address.getName() + " ");

System.out.print(address.getStreet() + " ");

System.out.print(address.getCity() + " ");

System.out.print(address.getState() + " ");

System.out.println(address.getZip());

}

System.out.println("------------ Update the Street as MNO for the Name :A -------------");

//pointing the file pointer back to start to update the the street as 'MNO' for name 'A'

raf.seek(0);

for (int i = 0; i < numRecords; i++) {

address.read(raf);

if (address.getName().trim().equals("A")) {

address.setStreet("MNO");

raf.seek(raf.getFilePointer() - address.size());

address.write(raf);

raf.seek(raf.getFilePointer() - address.size());

address.read(raf);

}

System.out.print(address.getName() + " ");

System.out.print(address.getStreet() + " ");

System.out.print(address.getCity() + " ");

System.out.print(address.getState() + " ");

System.out.println(address.getZip());

}

}

}

=======================================================================================

OUTPUT

A abc Boston LA 12345

B def Newyork CA 67891

C xyz Seatle NY 23456

------------------------- Update the Street as MNO for the name :A -------------------------------

A MNO Boston LA 12345

B def Newyork CA 67891

C xyz Seatle NY 23456