how to put user`s input to save as a file and repen a file after that...
hi all..this problem confuse me a lot ...pls give me some suggustion to solve this problem...i got a run-time problem after i compier my code
*****
Please enter your CD`s title : ivan
Please enter your CD`s Artist/GroupName : jdd
Please enter your CD`s year of release : 2009
Please enter your CD`s MusicGenre(e.g.: Jazz, Blues, Funk, Classical, Rock, etc...) : rock
Please enter your CD`s comment : jfjfw
Do you have another Cd ? (Y/N) : n
Saving to file
Exception in thread "main" java.lang.NullPointerException
at Demo.saveDate(Demo.java:48)
at Demo.readDataFromConsole(Demo.java:126)
at Demo.main(Demo.java:197)
>Exit code: 1
import java.util.ArrayList;
import java.io.*;
publicclass Demo{
readOperation theRo =new readOperation();
errorCheckingOperation theEco =new errorCheckingOperation();
ArrayList<MusicCd> MusicCdList;
public Demo()
{
}
privatevoid heading()
{
System.out.println("\tTesting read data from console, save to file, reopen that file\t");
}
privatevoid saveDate()
{
try
{
File f =new File("jessica.txt");
FileOutputStream fos =new FileOutputStream(f);
ObjectOutputStream oos =new ObjectOutputStream(fos);
oos.writeObject(new Integer(MusicCdList.size()));
for( MusicCd s : MusicCdList)
oos.writeObject(s);
oos.close();
}
catch (IOException ioe)
{
ioe.printStackTrace();
}
}
privatevoid loadDate()
{
MusicCdList =new ArrayList<MusicCd>( );
try
{
File g =new File("jessica.txt");
FileInputStream fis =new FileInputStream(g);
ObjectInputStream ois =new ObjectInputStream(fis);
ArrayList<String> stuff = (ArrayList<String>)ois.readObject();
for( String s : stuff ) System.out.println(s);
ois.close();
}catch (Exception ioe)
{
ioe.printStackTrace();
}
}
privatevoid readDataFromConsole()
//private void insertCd()
{
ArrayList<MusicCd> MusicCdList =new ArrayList<MusicCd>( );
readOperation theRo =new readOperation();
errorCheckingOperation theEco =new errorCheckingOperation();
MusicCd theCd;
String muiseCdsTitle;
String muiseCdsArtistOrGroupName;
int muiseCdsYearOfRelease;
int validMuiseCdsYearOfRelease;
String muiseCdsMusicGenre;
String muiseCdsAComment;
while(true)
{
String continueInsertCd ="Y";
do
{
muiseCdsTitle = theRo.readString("Please enter your CD`s title : ");
muiseCdsArtistOrGroupName = theRo.readString("Please enter your CD`s Artist/GroupName : ");
muiseCdsYearOfRelease = theRo.readInt("Please enter your CD`s year of release : ");
validMuiseCdsYearOfRelease = theEco.errorCheckingInteger(muiseCdsYearOfRelease, 1000, 9999);
muiseCdsMusicGenre = theRo.readString("Please enter your CD`s MusicGenre(e.g.: Jazz, Blues, Funk, Classical, Rock, etc...) : ");
muiseCdsAComment = theRo.readString("Please enter your CD`s comment : ");
MusicCdList.add(new MusicCd(muiseCdsTitle, muiseCdsArtistOrGroupName, validMuiseCdsYearOfRelease ,
muiseCdsMusicGenre, muiseCdsAComment));
MusicCdList.trimToSize();
//saveToFile(MusicCdList);
continueInsertCd = theRo.readString("Do you have another Cd ? (Y/N) : ");
}while(continueInsertCd.equals("Y") || continueInsertCd.equals("y") );
if(continueInsertCd.equals("N") || continueInsertCd.equals("n"));
{
System.out.println("Saving to file ");
//MusicCdList.add(new MusicCd(muiseCdsTitle, muiseCdsYearOfRelease));
saveDate();
loadDate();
break;
}
}
}
publicstaticvoid main(String[] args)
{
Demo one =new Demo();
one.readDataFromConsole();
}
}
The following code for better understnd of what i did
import java.util.*;
publicclass readOperation{
public String readString(String userInstruction)
{
String aString =null;
try
{
Scanner scan =new Scanner(System.in);
System.out.print(userInstruction);
aString = scan.nextLine();
}
catch (NoSuchElementException e)
{
//if no line was found
System.out.println("\nNoSuchElementException error occurred (no line was found) " + e);
}
catch (IllegalStateException e)
{
// if this scanner is closed
System.out.println("\nIllegalStateException error occurred (scanner is closed)" + e);
}
return aString;
}
publicchar readTheFirstChar(String userInstruction)
{
char aChar =' ';
String strSelection =null;
try
{
//char charSelection;
Scanner scan =new Scanner(System.in);
System.out.print(userInstruction);
strSelection = scan.next();
aChar = strSelection.charAt(0);
}
catch (NoSuchElementException e)
{
//if no line was found
System.out.println("\nNoSuchElementException error occurred (no line was found) " + e);
}
catch (IllegalStateException e)
{
// if this scanner is closed
System.out.println("\nIllegalStateException error occurred (scanner is closed)" + e);
}
return aChar;
}
publicint readInt(String userInstruction){
int aInt = 0;
try{
Scanner scan =new Scanner(System.in);
System.out.print(userInstruction);
aInt = scan.nextInt();
}catch (InputMismatchException e){
System.out.println("\nInputMismatchException error occurred (the next token does not match the Integer regular expression, or is out of range) " + e);
}catch (NoSuchElementException e){
System.out.println("\nNoSuchElementException error occurred (input is exhausted)" + e);
}catch (IllegalStateException e){
System.out.println("\nIllegalStateException error occurred (scanner is closed)" + e);
}
return aInt;
}
}
import java.io.Serializable;
publicclass MusicCdimplements Serializable
{
private String musicCdsTitle;// CD`s title
private String artistOrGroupName;// CD`s artist/GroupName,
privateint yearOfRelease;//CD`s yearOfRelease
private String musicGenre;//Cd`s music genre
private String aComment;
public MusicCd()
{
musicCdsTitle ="None";
artistOrGroupName ="None";
yearOfRelease = 1000;
musicGenre ="None";
aComment ="None";
}
public MusicCd(String newMusicCdsTitle, String newArtistOrGroupName,int newYearOfRelease,
String newMusicGenre, String aNewComment)
{
musicCdsTitle = newMusicCdsTitle;
artistOrGroupName = newArtistOrGroupName;
/*
if((newYearOfRelease >= 1000) && (newYearOfRelease <= 9999))
{
yearOfRelease = newYearOfRelease;
}
else
{
System.out.println("Invalid years..Try again!!");
// System.exit(0);
return;
}
*/
yearOfRelease = newYearOfRelease;
musicGenre = newMusicGenre;
aComment = aNewComment;
}
public String getTitle()
{
return musicCdsTitle;
}
public String getArtistOrGroupName()
{
return artistOrGroupName;
}
publicint getYearOfRelease()
{
return yearOfRelease;
}
public String getMusicGenre()
{
return musicGenre;
}
public String getAComment()
{
return aComment;
}
publicvoid setTitle(String newMusicCdsTitle)
{
musicCdsTitle = newMusicCdsTitle;
}
publicvoid setArtistOrGroupName(String newArtistOrGroupName)
{
artistOrGroupName = newArtistOrGroupName;
}
publicvoid setYearOfRelease(int newYearOfRelease)
{
yearOfRelease = newYearOfRelease;
}
publicvoid setMusicGenre(String newMusicGenre)
{
musicGenre = newMusicGenre;
}
publicvoid setAComment(String aNewComment)
{
aComment = aNewComment;
}
/*
public boolean equalsName(MusicCd otherCd)
{
if(otherCd == null)
return false;
else
return (musicCdsTitle.equals(otherCd.musicCdsTitle));
}
*/
public String toString()
{
return("Title: " + musicCdsTitle +"\t"
+"Artist/GroupName: " + artistOrGroupName +"\t"
+"Year of release: " + yearOfRelease +"\t"
+"Music Genre: " + musicGenre +"\t"
+"Comment: " + aComment +"\t" );
}
}
import java.util.Scanner;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;
publicclass errorCheckingOperation
{
publicint errorCheckingInteger(int checkThing,int lowerBound,int upperBound)
{
int aInt = checkThing;
try
{
while((checkThing < lowerBound ) || (checkThing > upperBound) )
thrownew Exception("Invaild value....Please enter the value between " + lowerBound +" & " + upperBound );
}
catch (Exception e)
{
String message = e.getMessage();
System.out.println(message);
}
return aInt;
}
publicint errorCheckingSelectionValue(String userInstruction)
{
int validSelectionValue = 0;
try
{
int selectionValue;
Scanner scan =new Scanner(System.in);
System.out.print(userInstruction);
selectionValue = scan.nextInt();
validSelectionValue = errorCheckingInteger(selectionValue , 1, 5);
}
catch (NoSuchElementException e)
{
//if no line was found
System.out.println("\nNoSuchElementException error occurred (no line was found) " + e);
}
catch (IllegalStateException e)
{
// if this scanner is closed
System.out.println("\nIllegalStateException error occurred (scanner is closed)" + e);
}
return validSelectionValue;
}
}
