Modify Record Number in a Random Access File
Hi Does anyone know if I can modify the record number in the random access file hardware.dat for each hardware record each time and update it in hardware.dat to display it? Also why does it say "Record does not exist" if I modify the record number for a hardware and try to update it but could not find that record?
Here is the code below:
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// Exercise 14.11: HardwareRecord.java
package org.egan;// packaged for reuse
publicclass HardwareRecord
{
privateint recordNumber;
private String toolName;
privateint quantity;
privatedouble cost;
// no-argument constructor calls other constructor with default values
public HardwareRecord()
{
this(0,"",0,0.0);// call four-argument constructor
}// end no-argument HardwareRecord constructor
// initialize a record
public HardwareRecord(int number, String tool,int amount,double price)
{
setRecordNumber(number);
setToolName(tool);
setQuantity(amount);
setCost(price);
}// end four-argument HardwareRecord constructor
// set record number
publicvoid setRecordNumber(int number)
{
recordNumber = number;
}// end method setRecordNumber
// get record number
publicint getRecordNumber()
{
return recordNumber;
}// end method getRecordNumber
// set tool name
publicvoid setToolName(String tool)
{
toolName = tool;
}// end method setToolName
// get tool name
public String getToolName()
{
return toolName;
}// end method getToolName
// set quantity
publicvoid setQuantity(int amount)
{
quantity = amount;
}// end method setQuantity
// get quantity
publicint getQuantity()
{
return quantity;
}// end method getQuantity
// set cost
publicvoid setCost(double price)
{
cost = price;
}// end method setCost
// get cost
publicdouble getCost()
{
return cost;
}// end method getCost
}// end class HardwareRecord
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// Exercise 14.11: RandomAccessHardwareRecord.java
// Subclass of HardwareRecord for random-access file programs.
package org.egan;// package for reuse
import java.io.RandomAccessFile;
import java.io.IOException;
publicclass RandomAccessHardwareRecordextends HardwareRecord
{
publicstaticfinalint SIZE = 46;
// no-argument constructor calls other constructor with default values
public RandomAccessHardwareRecord()
{
this(0,"",0,0.0);
}// end no-argument RandomAccessHardwareRecord constructor
// initialize a RandomAccessHardwareRecord
public RandomAccessHardwareRecord(int number, String tool,int amount,double price)
{
super(number,tool,amount,price);
}// end four-argument RandomAccessHardwareRecord constructor
// read a record from a specified RandomAccessFile
publicvoid read(RandomAccessFile file)throws IOException
{
setRecordNumber(file.readInt());
setToolName(readName(file));
setQuantity(file.readInt());
setCost(file.readDouble());
}// end method read
// ensure that name is proper length
private String readName(RandomAccessFile file)throws IOException
{
char name[] =newchar[15], temp;
for(int count = 0; count < name.length; count++)
{
temp = file.readChar();
name[count] = temp;
}// end for
returnnew String(name).replace('\0',' ');
}// end method readName
// write a record to specified RandomAccessFile
publicvoid write(RandomAccessFile file)throws IOException
{
file.writeInt(getRecordNumber());
writeName(file, getToolName());
file.writeInt(getQuantity());
file.writeDouble(getCost());
}// end method write
// write a name to file; maximum of 15 characters
privatevoid writeName(RandomAccessFile file, String name)throws IOException
{
StringBuffer buffer =null;
if (name !=null)
buffer =new StringBuffer(name);
else
buffer =new StringBuffer(15);
buffer.setLength(15);
file.writeChars(buffer.toString());
}// end method writeName
}// end RandomAccessHardwareRecord
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// Exercise 14.11: CreateRandomFile.java
// creates random-access file by writing 100 empty records to disk.
import java.io.IOException;
import java.io.RandomAccessFile;
import org.egan.RandomAccessHardwareRecord;
publicclass CreateRandomFile
{
privatestaticfinalint NUMBER_RECORDS = 100;
// enable user to select file to open
publicvoid createFile()
{
RandomAccessFile file =null;
try// open file for reading and writing
{
file =new RandomAccessFile("hardware.dat","rw");
RandomAccessHardwareRecord blankRecord =new RandomAccessHardwareRecord();
// write 100 blank records
for (int count = 0; count < NUMBER_RECORDS; count++)
blankRecord.write(file);
// display message that file was created
System.out.println("Created file hardware.dat.");
System.exit(0);// terminate program
}// end try
catch (IOException ioException)
{
System.err.println("Error processing file.");
System.exit(1);
}// end catch
finally
{
try
{
if (file !=null)
file.close();// close file
}// end try
catch (IOException ioException)
{
System.err.println("Error closing file.");
System.exit(1);
}// end catch
}// end finally
}// end method createFile
}// end class CreateRandomFile
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// Exercise 14.11: CreateRandomFileTest.java
// Testing class CreateRandomFile
publicclass CreateRandomFileTest
{
// main method begins program execution
publicstaticvoid main( String args[] )
{
CreateRandomFile application =new CreateRandomFile();
application.createFile();
}// end main
}// end class CreateRandomFileTest
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// Exercise 14.11: MenuOption.java
// Defines an enum type for the hardware credit inquiry program's options.
publicenum MenuOption
{
// declare contents of enum type
PRINT(1),
UPDATE(2),
NEW(3),
DELETE(4),
END(5);
privatefinalint value;// current menu option
MenuOption(int valueOption)
{
value = valueOption;
}// end MenuOptions enum constructor
publicint getValue()
{
return value;
}// end method getValue
}// end enum MenuOption
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// Exercise 14.11: FileEditor.java
// This class declares methods that manipulate hardware account records
// in a random access file.
import java.io.EOFException;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Scanner;
import org.egan.RandomAccessHardwareRecord;
publicclass FileEditor
{
RandomAccessFile file;// reference to the file
Scanner input =new Scanner(System.in);
// open the file
public FileEditor(String fileName)throws IOException
{
file =new RandomAccessFile(fileName,"rw");
}// end FileEditor constructor
// close the file
publicvoid closeFile()throws IOException
{
if (file !=null)
file.close();
}// end method closeFile
// get a record from the file
public RandomAccessHardwareRecord getRecord(int recordNumber)
throws IllegalArgumentException, NumberFormatException, IOException
{
RandomAccessHardwareRecord record =new RandomAccessHardwareRecord();
if (recordNumber < 1 || recordNumber > 100)
thrownew IllegalArgumentException("Out of range");
// seek appropriate record in a file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record.read(file);
return record;
}// end method getRecord
// update record tool name in file
publicvoid updateRecordToolName(int recordNumber, String newToolName)
throws IllegalArgumentException, IOException
{
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() == 0)
thrownew IllegalArgumentException("Record does not exist");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record.setToolName(newToolName);
record =new RandomAccessHardwareRecord(
record.getRecordNumber(), record.getToolName(), record.getQuantity(), record.getCost());
record.write(file);// write updated record to file
}// end method updateRecordToolName
// update record in file
publicvoid updateRecordQuantity(int recordNumber,int newQuantity)
throws IllegalArgumentException, IOException
{
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() == 0)
thrownew IllegalArgumentException("Record does not exist");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record.setQuantity(newQuantity);
record =new RandomAccessHardwareRecord(
record.getRecordNumber(), record.getToolName(), record.getQuantity(), record.getCost());
record.write(file);// write updated record to file
}// end method updateRecordQuantity
// update record in file
publicvoid updateRecordCost(int recordNumber,double newCost)
throws IllegalArgumentException, IOException
{
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() == 0)
thrownew IllegalArgumentException("Record does not exist");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record.setCost(newCost);
record =new RandomAccessHardwareRecord(
record.getRecordNumber(), record.getToolName(), record.getQuantity(), record.getCost());
record.write(file);// write updated record to file
}// end method updateRecordCost
// add record to file
publicvoid newRecord(int recordNumber, String toolName,int quantity,double cost)
throws IllegalArgumentException, IOException
{
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() != 0)
thrownew IllegalArgumentException("Record already exists");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
record =new RandomAccessHardwareRecord(recordNumber, toolName, quantity, cost);
record.write(file);// write record to file
}// end method newRecord
// delete record from file
publicvoid deleteRecord(int recordNumber)throws IllegalArgumentException, IOException
{
RandomAccessHardwareRecord record = getRecord(recordNumber);
if (record.getRecordNumber() == 0)
thrownew IllegalArgumentException("Account does not exist");
// seek appropriate record in file
file.seek((recordNumber - 1) * RandomAccessHardwareRecord.SIZE);
// create a blank record to write to the file
record =new RandomAccessHardwareRecord();
record.write(file);
}// end method deleteRecord
// read and display records
publicvoid readRecords()
{
RandomAccessHardwareRecord record =new RandomAccessHardwareRecord();
System.out.printf("%-10s%-15s%-15s%10s\n","Record","Tool Name","Quantity","Cost");
try// read a record and display
{
file.seek(0);
while (true)
{
do
{
record.read(file);
}
while (record.getRecordNumber() == 0);
// display record contents
System.out.printf("%-10d%-15s%-15d%10.2f\n",record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
}// end while
}// end try
catch (EOFException eofException)// close file
{
return;// end of file was reached
}// end catch
catch (IOException ioException)
{
System.err.println("Error reading file.");
System.exit(1);
}// end catch
}// end method readRecords
}// end class FileEditor
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// Exercise 14.11: TransactionProcessor.java
// A transaction processing program using random-access files.
import java.io.IOException;
import java.util.NoSuchElementException;
import java.util.Scanner;
import org.egan.RandomAccessHardwareRecord;
publicclass TransactionProcessor
{
private FileEditor dataFile;
private RandomAccessHardwareRecord record;
private MenuOption choices[] ={MenuOption.PRINT, MenuOption.UPDATE, MenuOption.NEW,
MenuOption.DELETE, MenuOption.END};
private Scanner input =new Scanner(System.in);
// get the file name and open the file
privateboolean openFile()
{
try// attempt to open file
{
// call the helper method to open the file
dataFile =new FileEditor("hardware.dat");
}// end try
catch (IOException ioException)
{
System.err.println("Error opening file.");
returnfalse;
}// end catch
returntrue;
}// end method openFile
// close file and terminate application
privatevoid closeFile()
{
try// close file
{
dataFile.closeFile();
}// end try
catch (IOException ioException)
{
System.err.println("Error closing file.");
System.exit(1);
}// end catch
}// end method closeFile
// create, update or delete the record
privatevoid performAction(MenuOption action)
{
int recordNumber = 0;// record number of record
String toolName;// tool name of the hardware instrument
int quantity;// total amount of items
double cost;// hareware tool price
int choice;// choose an update option
int newRecordNumber;// the updated record number
String newToolName;// the updated tool name
int newQuantity;// the updated quantity
double newCost;// the updated cost
try// attempt to manipulate files based on option selected
{
switch(action)// switch based on option selected
{
case PRINT:
System.out.println();
dataFile.readRecords();
break;
case NEW:
System.out.printf("\n%s%s\n%s\n%s","Enter record number,",
"tool name, quantity, and cost.","(Record number must be 1 - 100)","? ");
recordNumber = input.nextInt();// read record number
toolName = input.next();// read tool name
quantity = input.nextInt();// read quantity
cost = input.nextDouble();// read cost
dataFile.newRecord(recordNumber, toolName, quantity, cost);// create new record
break;
case UPDATE:
System.out.print("\nEnter record number to update (1 - 100): ");
recordNumber = input.nextInt();
record = dataFile.getRecord(recordNumber);
if (record.getRecordNumber() == 0)
System.out.println("Record does not exist.");
else
{
// display record contents
System.out.printf("%-10d%-12s%-12d%10.2f\n\n", record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
System.out.printf("%s%s","\nEnter 1 to update tool name, ",
"2 to update quantity, or 3 to update cost : ");
choice = input.nextInt();
if (choice == 1)
{
System.out.print("Enter new record tool name : ");
newToolName = input.next();
dataFile.updateRecordToolName(recordNumber,newToolName);// update record
// tool name
// retrieve updated record
record = dataFile.getRecord(recordNumber);
// display updated record
System.out.printf("%-10d%-12s%-12d%10.2f\n", record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
}
elseif (choice == 2)
{
System.out.print("Enter new record quantity : ");
newQuantity = input.nextInt();
dataFile.updateRecordQuantity(recordNumber,newQuantity);// update record
// quantity
// retrieve updated record
record = dataFile.getRecord(recordNumber);
// display updated record
System.out.printf("%-10d%-12s%-12d%10.2f\n", record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
}
elseif (choice == 3)
{
System.out.print("Enter new record cost : ");
newCost = input.nextDouble();
dataFile.updateRecordCost(recordNumber,newCost);// update record cost
// retrieve updated record
record = dataFile.getRecord(recordNumber);
// display updated record
System.out.printf("%-10d%-12s%-12d%10.2f\n", record.getRecordNumber(),
record.getToolName(), record.getQuantity(), record.getCost());
}
}// end else
break;
case DELETE:
System.out.print("\nEnter an account to delete ( 1 - 100): ");
recordNumber = input.nextInt();
dataFile.deleteRecord(recordNumber);// delete record
break;
default:
System.out.println("Invalid action.");
break;
}// end switch
}// end try
catch (NumberFormatException format)
{
System.err.println("Bad input.");
}// end catch
catch (IllegalArgumentException badRecord)
{
System.err.println(badRecord.getMessage());
}// end catch
catch (IOException ioException)
{
System.err.println("Error writing to the file.");
}// end catch
catch (NoSuchElementException elementException)
{
System.err.println("Invalid input. Please try again.");
input.nextLine();
}// end catch
}// end method performAction
// enable user to input menu choice
private MenuOption enterChoice()
{
int menuChoice = 1;
// display available options
System.out.printf("\n%s\n%s\n%s\n%s\n%s\n%s","Enter your choice",
"1 - List hardware records","2 - Update a hardware record",
"3 - Add a new hardware record","4 - Delete a hardware record","5 - End program\n?");
try
{
menuChoice = input.nextInt();
}
catch (NoSuchElementException elementException)
{
System.err.println("Invalid input.");
System.exit(1);
}// end catch
return choices[menuChoice - 1];// return choice from user
}// end enterChoice
publicvoid processRequests()
{
openFile();
// get user's request
MenuOption choice = enterChoice();
while (choice != MenuOption.END)
{
performAction(choice);
choice = enterChoice();
}// end while
closeFile();
}// end method processRequests
}// end class TransactionProcessor
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// Exercise 14.11: TransactionProcessorTest.java
// Testing the transaction processor.
publicclass TransactionProcessorTest
{
publicstaticvoid main(String args[])
{
TransactionProcessor application =new TransactionProcessor();
application.processRequests();
}// end main
}// end class TransactionProcessorTest
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Below is the sample data to be entered into the random input file hardware.dat :
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Record ToolQuantityCost
NumberName
3 Sander18 35.99
19 Hammer128 10.00
26 Jigsaw1614.25
39 Mower1079.50
56 Saw8 89.99
76 Screwdriver236 4.99
81 Sledgehammer3219.75
88 Wrench 656.48
Message was edited by:
egan128
Message was edited by:
egan128
Message was edited by:
egan128
