Authors:
Walter Savitch ,kenrick Mock
Chapter:
File Io
Exercise:
Programming Projects
Question:11 | ISBN:9780132830317 | Edition: 5
Question
Change the definition of the class Person in Display 5.19 to be serializable. Note that this requires that you also change the class Date . Then write a program to maintain a binary file of records of people (records of type Person ). Allow commands to delete a record specified by the person’s name, to add a record, to retrieve and display a record, and to obtain all records of people within a specified age range. To obtain the age of a person, you need the current date. Your program will ask the user for the current date when the program begins. You can do this with random access files, but do not use random access files for this exercise. Use a file or files that record records with the method writeObject of the class ObjectOutputStream .
Answer
Take Person,Date codes from the Display 5.19 in text book.
The following code is main class code:
import java.io.*;
import java.util.*;
public class PersonDemo
{
public static void main(String args[])
{
Scanner scan = new Scanner(System.in);
int ch = 0;
System.out.println("Enter current date: ");
Date currentDate = new Date();
currentDate.readInput();
while(ch != -1)
{
System.out.println("1) Add Record");
System.out.println("2) Delete Record");
System.out.println("3) Display Record");
System.out.println("4) Obtain Record within age");
System.out.println("-1) Exit");
System.out.print("Enter choice: ");
ch = scan.nextInt();
scan.nextLine();
ObjectInputStream inputStream = null;
ObjectOutputStream outputStream = null;
switch(ch)
{
case 1:
try
{
try
{
outputStream =new ObjectOutputStream(new FileOutputStream("peopleTemp.dat"));
inputStream = new ObjectInputStream(new FileInputStream("people.dat"));
while(true)
{
Person current =(Person)inputStream.readObject();
outputStream.writeObject(current);
}
}
catch(IOException e)
{
}
try
{
outputStream = new ObjectOutputStream(new FileOutputStream("people.dat"));
inputStream = new ObjectInputStream(new FileInputStream("peopleTemp.dat"));
while(true)
{
Person current =(Person)inputStream.readObject();
outputStream.writeObject(current);
}
}
catch(IOException e)
{
}
System.out.print(
"Enter name of person:");
String name = scan.nextLine();
System.out.println("Enter birth date:");
Date birthDate = new Date();
birthDate.readInput();
Date deathDate = new Date();
System.out.println("Is the person still alive? (y/n)");
String answer = scan.nextLine();
if(answer.equals("y"))
deathDate = null;
else
{
System.out.println("Enter death date :");
deathDate.readInput();
}
outputStream.writeObject(new Person(name, birthDate, deathDate));
}
System.out.println();
break;
case 2: //Deleting a person
try
{
System.out.println("Enter the name of person to be removed:");
String nameToRemove = scan.nextLine();
outputStream = new ObjectOutputStream(new FileOutputStream("peopleTemp.dat"));
inputStream = new ObjectInputStream(new FileInputStream("people.dat"));
while(true)
{
Person current = (Person)inputStream.readObject();
if(!current.getName().equals(nameToRemove))
outputStream.writeObject(current);
}
}
catch (ClassNotFoundException e)
{
System.out.println("Error: person not found.");
}
catch(IOException e)
{
}
try
{
outputStream = new ObjectOutputStream(new FileOutputStream("people.dat"));
inputStream = new ObjectInputStream(new FileInputStream("peopleTemp.dat"));
while(true)
{
outputStream.writeObject((Person)inputStream.readObject());
}
}
catch (ClassNotFoundException e)
{
System.out.println("Error: person not found.");
}
catch (IOException e)
{
System.out.println("Successfully removed person with specified name.");
}
System.out.println();
break;
case 3: //Displaying a person's record
try
{
System.out.print("Enter name of person to read record: ");
String nameToDisplay = scan.nextLine();
inputStream = new ObjectInputStream(new FileInputStream("people.dat"));
while(true)
{
Person current = (Person)inputStream.readObject();
if(current.getName().equals(nameToDisplay))
System.out.println(current.toString());
}
}
catch (ClassNotFoundException e)
{
System.out.println( "Error: person not found.");
}
catch(IOException e)
{
}
System.out.println();
break;
case 4:
System.out.println("Enter first number of the age range: ");
int age1 = scan.nextInt();
System.out.println("Enter second number:");
int age2 = scan.nextInt();
try
{
inputStream = new ObjectInputStream(new FileInputStream("people.dat"));
while(true)
{
Person current = (Person)inputStream.readObject();
Date birth = current.getBirthDate();
Date death = current.getDeathDate();
int age;
if(death != null)
{
age = death.getYear() – birth.getYear();
if(death.precedes(birth))
age--;
}
else
{
age = currentDate.getYear() – birth.getYear();
if(currentDate.precedes(birth))
age--;
}
if(age >= age1 || age <= age2)
System.out.println(current.toString());
}
}
catch (ClassNotFoundException e)
{
System.out.println("Error: person not found.");
}
catch(IOException e)
{
}
System.out.println();
break;
case -1:
break;
default:
System.out.println("Invalid choice.");
System.out.println();
break;
}
if(inputStream != null)
try
{
inputStream.close();
}
catch (IOException e)
{
}
if(outputStream != null)
try
{
outputStream.close();
}
catch (IOException e)
{
}
}
}
}