This is a college course assignment that creates a ItemRecord class and implements Serializable with getter and setters, then overrides the toString method. Next I created a ItemRecordReport class with a Scanner object mapped to an input file "ItemRecord_text.txt". Created an ObjectOutputStream object mapped to a binary output file "ItemRecord_binary.txt". Created an ObjectInputStream object mapped to the binary file. Everything works. I modified this post by putting in an array in method main and changing the field values with a additional text document. My error is a NullPointerException: This is the stack trace
Item Cost Quantity Description
Number
A100 $ 99.99 10 Canon PowerShot-135
A200 $149.99 50 Panasonic-Lumix T55
A300 $349.99 20 Nikon- D3200 DSRL
A400 $280.99 30 Sony- DSC-W800
A500 $ 97.99 20 Samsung- WB35F
Exception in thread "main" java.lang.NullPointerException
at ItemRecordReport.endRecord(ItemRecordReport.java:165)
at ItemRecordReport.main(ItemRecordReport.java:156)
----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.
//create program so that objects of class can be serialized, implements interface Serialiable //create constructor with 4 parameters with accompanying get and set methods, Override toString method //create text file with 5 records, create Scanner object,ObjectOutputStream, and ObjectInputStream //create new ItemRecord object, change values of all fields in ItemRecord object using object's set methods //modify ItemRecord object using toString method
import java.io.Serializable;
public class ItemRecord implements Serializable
{ //declare 4 fields with private access
private String itemNumber;
private double cost;
private int quantity;
private String description;
//constructor with no arguments call other constructor with default values
public ItemRecord()
{
this("",0.0,0,"");
}//end constructor with no arguments
//constructor with 4 arguments
public ItemRecord(String number, double price, int quant, String desc)
{
setItemNumber(number);
setCost(price);
setQuantity(quant);
setDescription(desc);
}//end constructor
public void setItemNumber(String number)
{
itemNumber = number;
}//end setItemNumber
public String getItemNumber()
{
return itemNumber;
}//end getItemNumber
public void setCost(double price)
{
cost = price;
}//end seCost
public double getCost()
{
return cost;
}//end getCost
public void setQuantity(int quant)
{
quantity = quant;
}//end setQuantity
public int getQuantity()
{
return quantity;
}//end getQuantity
public void setDescription(String desc)
{
description = desc;
}//end setDescription
public String getDescription()
{
return description;
}//end getDescription
public static void printHeading()
{
System.out.println("Item Cost Quantity Description");
System.out.print("Number");
System.out.println();
}
public String toString()
{
return this.getItemNumber()+String.format(" $%6.2f ",+this.getCost())+String.format("%4d ",+this.getQuantity())+this.getDescription();
}
}//end class ItemRecord
Here is the other test class: This class contain the ObjectOutputStream and ObjectInputStream objects. Therefore method main is here as well as the ItemRecordReport object that I use to call the methods in main.
import java.io.*;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.Scanner;
public class ItemRecordReport
{ private ObjectOutputStream output;//writes to binary
private ObjectInputStream binInFile;//reads binary
private Scanner input;
public void openInputBinaryFile()
{//create a ObjectInputStream object that will read a binary file
try
{
binInFile = new ObjectInputStream(new FileInputStream("ItemRecord_binary.txt"));
}//end try
catch (IOException ioException)
{
System.out.println("Error opening file.");
}//end catch
}//end openInputBinaryFile
public void openOutputBinaryFile()
{
//creating a binary objectOutputStream text file
try
{
output = new ObjectOutputStream(
new FileOutputStream("ItemRecord_binary.txt"));
}//end try
catch (IOException ioException)
{
System.err.println("Error opening file");
}
}//end openOutputBinaryFile
public void readInputTextRecords()
{
ItemRecord record;
String itemNumber;
double cost;
int quantity;
String description;
try
{
input = new Scanner(new File("ItemRecord_text.txt"));
}
catch (IOException e)
{
System.out.println("Error file not found");
}//end catch
while(input.hasNext())
{
try{
itemNumber = input.next();
cost = input.nextDouble();
quantity = input.nextInt();
description = input.nextLine();
record = new ItemRecord(itemNumber,cost,quantity,description);
//writing into the binary text file
output.writeObject(record);
}
catch (IOException ioException)
{
System.out.println("Error writing to binary file.");
return;
}
}
}//end readInputRecords
public void readInputBinaryRecords()
{
openInputBinaryFile();
ItemRecord otherRecord;
try
{ while (true)
{
otherRecord = (ItemRecord) binInFile.readObject(); //use down cast
System.out.println(otherRecord.toString());
}
}
catch (EOFException e)
{
return;
}//end catch
catch (ClassNotFoundException e)
{
System.err.println("Unable to create object.");
}//end catch
catch (IOException ioException)
{
System.err.println("Error reading from binary file.");
}//end catch
}//readInputBinaryRecords
public void closeBinaryOutputFile()
{
try
{ if (output !=null )
output.close();
}//end try
catch ( IOException ioException)
{
System.out.println( "Error closing file");
System.exit(1);
}//end catch
}//end closeBinaryOutputFile
public void closeBinaryInputFile()
{
try
{ if (binInFile != null )
binInFile.close();
else
System.out.println("No records were written to the binary file!");
}//end try
catch ( IOException ioException)
{
System.out.println( "Error closing file");
System.exit(1);
}//end catch
}//end closeBinaryFile
public static void main(String[] args)
{
ItemRecordReport object = new ItemRecordReport();
ItemRecord.printHeading();//print heading
object.openOutputBinaryFile();//opens the binary file
object.readInputTextRecords();//reads text file and writes to binary file
object.closeBinaryOutputFile();//closes the binaryOutputFile
object.openInputBinaryFile();//opens binary file
object.readInputBinaryRecords();
object.closeBinaryInputFile();
Scanner inFile;
ItemRecord[] itemRecord = new ItemRecord[5];
itemRecord[x] = new ItemRecord();
for (int x = 0; x <= 4; x++){
itemRecord[x].setItemNumber("");
itemRecord[x].setCost(0);
itemRecord[x].setQuantity(0);
itemRecord[x].setDescription("");
}
try
{
inFile = new Scanner(new File("itemRecord.txt"));
while(inFile.hasNext())
{
for(int count =0; count<=4; count++)
{
itemRecord[count].setItemNumber(inFile.next());
itemRecord[count].setCost(inFile.nextDouble());
itemRecord[count].setQuantity(inFile.nextInt());
itemRecord[count].setDescription(inFile.next());
}//end for loop
}//end while
}
catch (IOException e)
{
System.out.println("Error file not found");
}//end catch
try
{
ObjectOutputStream binOutFile = new ObjectOutputStream
(new FileOutputStream("ItemRecord_binary.txt"));
}//end try
catch (IOException e)
{
System.err.println("error opening file");
}
System.out.println(itemRecord.toString());
}//end method main
}//end class ItemRecordReport
And here is the text file:
A100 99.99 10 Canon PowerShot-135
A200 149.99 50 Panasonic-Lumix T55
A300 349.99 20 Nikon- D3200 DSRL
A400 280.99 30 Sony- DSC-W800
A500 97.99 20 Samsung- WB35F
This is the new text file to change the field values:
B100 98.00 10 ABC1010
B200 97.00 15 DEF1020
B300 96.00 10 GHI1030
B400 95.00 05 JKL1040
B500 94.00 01 MNO1050
Error stack trace
Item Cost Quantity Description
Number
A100 $ 99.99 10 Canon PowerShot-135
A200 $149.99 50 Panasonic-Lumix T55
A300 $349.99 20 Nikon- D3200 DSRL
A400 $280.99 30 Sony- DSC-W800
A500 $ 97.99 20 Samsung- WB35F
Exception in thread "main" java.lang.NullPointerException
at ItemRecordReport.endRecord(ItemRecordReport.java:165)
at ItemRecordReport.main(ItemRecordReport.java:156)
----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.
