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Reading and writing object array list to text file

public void readList () {
try {
FileOutputStream writeData = new FileOutputStream("Accounts.txt");
ObjectOutputStream writeStream = new ObjectOutputStream(writeData);
writeStream.writeObject(AccountCredentials);
writeStream.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
public void writeList() {
try {
FileInputStream readData = new FileInputStream("Accounts.txt");
ObjectInputStream readStream = new ObjectInputStream(readData);
AccountCredentials = (ArrayList <Accounts>) readStream.readObject();
readStream.close();
System.out.println(AccountCredentials.size());
}
catch (Exception e) {
e.printStackTrace();
}
}
My readList method works fine right, I have ¬í sr java.util.ArrayListxÒ™Ça I sizexp w
in the file. My writeList does not. I have a School folder inside the Netbeans folder, and in the main directory is Accounts.txt. Do I need to specify that? My Java file is in Schools/src. It always says my list size is 0

Can you please share the exception or stack trace you are getting and paste it here ? , Also I would highly recommend not to use a flat file for storing the account credentials, rather use any of the identity management solution and db driven account management. Did you also try to debug the following line "ObjectInputStream readStream = new ObjectInputStream(readData);"

OutofMemory error while writing a large file Android

I'm trying to encrypt a large file which is 500MB but my code throws an out of memory error, for small files below 50MB the code works fine. Im using a third party library called JNCryptor for encryption, please have a look at my code and correct me if any mistake. Thanks in advance.
public void encrypt() {
String file = Environment.getExternalStorageDirectory() + "/sai/ravi_enc.exe";
byte[] filedata = null;
try {
filedata = IOUtils.toByteArray(new FileInputStream(file));
} catch (IOException e) {
e.printStackTrace();
}
JNCryptor cryptor = new AES256JNCryptor();
String password = "123456789";
try {
byte[] ciphertext = cryptor.decryptData(filedata, password.toCharArray());
String Outfile = Environment.getExternalStorageDirectory() + "/sai/ravi_dec.exe";
writeFile(ciphertext, Outfile);
System.out.println("Done");
} catch (CryptorException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void writeFile(byte[] data, String fileName) throws IOException {
FileOutputStream out = new FileOutputStream(fileName);
out.write(data);
out.close();
}

This is up to JNCryptor to well manage memory, especially if it uses temp buffer. It is better to work on streams instead of buffers. Just for testing, if you write directly the fileData to your outFile, do you get OutOfMemoryError?
writeFile(filedata, Outfile);

Transferring data from input to output File, getting Exception

My data is not getting transferred to the output file , I always get an Exception.
import java.io.*;
import java.util.*;
class TransferData {
public static void main(String[] args) {
String path1="E:\\IO\\Input.txt";
String path2="E:\\IO\\Output.txt";
int data;
System.out.println("Transfering started...");
try {
FileInputStream fis=new FileInputStream(path1);
FileOutputStream fos=new FileOutputStream(path2);
while((data=fis.read())!=-1) {
fos.write(data);
}
}
catch(Exception e) {
System.out.println("exception caught!");
}
System.out.println("Completed...");
}
}
How do I transfer data to output file ?

Tested this code on my local machine it is works without exceptions.
Check is file E:/IO/Input.txt exists.
IS Directory E:/IO is writeable for your user
(If file E:/IO/Output.txt already exists check is it writeable and not opened in another programm)
By code:
It is good practice to close FIS and FOS after programm finished execution.
public class TransferData {
public static void main(String[] args) {
String path1 = "E:\\IO\\Input.txt";
String path2 = "E:\\IO\\Output.txt";
int data;
System.out.println("Transfering started...");
FileInputStream fis = null;
FileOutputStream fos = null;
try {
fis = new FileInputStream(path1);
fos = new FileOutputStream(path2);
while ((data = fis.read()) != -1) {
fos.write(data);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (fis != null) {
fis.close();
}
if (fos != null) {
fos.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
System.out.println("Completed...");
}
}

If you replace System.out.println("exception caught!"); with e.printStackTrace(); then you will get a much more useful error message.
If you then post that error message here, people will be able to help you much more easily.
It could be the case that the program cannot find the file you're trying to read.

I highly suggest to use e.printStackTrace() as the others suggested.
One possible problem might be the filesystem permissions or the file you are trying to read from being not existent.
You might also want to use a "try with resources" to simplify your code.
Your code is missing a close statement for your Streams too.
All together your code would look something like this:
import java.io.*;
import java.util.*;
class TransferData {
public static void main(String[] args) {
String path1="E:\\IO\\Input.txt";
String path2="E:\\IO\\Output.txt";
int data;
System.out.println("Transfering started...");
try (
FileInputStream fis=new FileInputStream(path1);
FileOutputStream fos=new FileOutputStream(path2)
) {
while((data=fis.read())!=-1) {
fos.write(data);
}
}
catch(Exception e) {
e.printStackTrace();
}
}
}
One last thing, if you post your code on StackOverflow, please do not mix different formatting styles (e.g. { in the same line as an if and sometimes in the next) and try to have the code well formatted from the beginning.

Add e.printStackTrace() to your catch block, and post the data printed in your console here, people will be able to help you better.
The most likely cause of the exception getting thrown is that the system is not able to find the file "E:\\IO\\Input.txt" or "E:\\IO\\Output.txt" make sure that the file's are there and Output.txt is not set to read only.

Java Android working with InputStream and File

Well, first of all, I'm just learning and don't quite understand what I'm doing.
What I want is to create an Excel file in memory and then it would be possible to send it with ActionBarSherlock's ShareActionProvider to mail for example.
But I got exeption :
11-24 18:45:52.112: W/System.err(22073): java.io.FileNotFoundException: /Competition.xls: open failed: EROFS (Read-only file system)
As I searched for the answer on the web - it's the problem of file being created in the system area which is read-only. But I want to create it in memory.. Somehow. Once again, I don't really understand well how it works - the way I see it - I create .xls file somewhere in the memory. So the explanation would be helpful.
So, here's the code :
private void createFileTosend() {
InputStream inputStream = null;
FileOutputStream outputStream = null;
try {
File toSend=null;
try {
toSend = getFile();
} catch (WriteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
inputStream = new BufferedInputStream(new FileInputStream(toSend));
outputStream = openFileOutput("Competition.xls",
Context.MODE_WORLD_READABLE | Context.MODE_APPEND);
byte[] buffer = new byte[1024];
int length = 0;
try {
while ((length = inputStream.read(buffer)) > 0){
outputStream.write(buffer, 0, length);
}
} catch (IOException ioe) {
/* ignore */
}
} catch (FileNotFoundException fnfe) {
/* ignore */
} finally {
try {
inputStream.close();
} catch (IOException ioe) {
/* ignore */
}
try {
outputStream.close();
} catch (IOException ioe) {
/* ignore */
}
}
}
public File getFile() throws IOException, WriteException{
File file=new File("Competition.xls");
WritableWorkbook workbook = Workbook.createWorkbook(file);
//then goes creation of Excel 's xls file which is not important for the question
workbook.write();
workbook.close();
return file;
}
Once again, don't downvote me, please, I'm just learning

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
Ass per the error log you post, i guess you didn't read it carefully. IT is saying read only file system. You need to put the above permission ATLEAST in your android manifest.
Do this much and see if there is any more error or not

I have a doubt may be wrong
outputStream = openFileOutput("Competition.xls",
Context.MODE_WORLD_READABLE | Context.MODE_APPEND);
you are using Context.MODE_WORLD_READABLE its readable, so how can you access it in write mode later. Is it right?
Check this link
Use the http://developer.android.com/guide/topics/data/data-storage.html to clear your doubt about file creation

Can't delete the file after writing some data to it, where is wrong?

I'm write some text a file then delete it, but the deletion is failed.
The code is very simple:
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
public class TestFile {
public static void main(String[] args) throws IOException {
File file = new File("c:\\abc.txt");
writeFile(file, "hello");
// delete the file
boolean deleted = file.delete();
System.out.println("Deleted? " + deleted);
}
public static void writeFile(File file, String content) throws IOException {
OutputStream out = null;
try {
out = new FileOutputStream(file);
out.write(content.getBytes("UTF-8"));
} catch (IOException e) {
try {
out.close();
} catch (IOException e1) {
// ignored
}
}
}
}
The output is:
Deleted? false
And there is a file abc.txt contains hello still there under c:.
Then I use FileUtils.writeStringToFile(...) from commons-io.jar instead, the file will be deleted.
But I don't know where is wrong with my code, please help me to find it out.

You are only closing the file if you get an IOException.
Change it to a finally block and you will be able to close and delete the file.
public static void writeFile(File file, String content) throws IOException {
OutputStream out = new FileOutputStream(file);
try {
out.write(content.getBytes("UTF-8"));
} finally {
try {
out.close();
} catch (IOException ignored) {
}
}
}

You need to close your OutputStream when you finished writing the file.
try {
out = new FileOutputStream(file);
out.write(content.getBytes("UTF-8"));
out.close();
} catch (IOException e) {
try {
out.close();
} catch (IOException e1) {
// ignored
}
}

In your main method,
public static void main(String[] args) throws IOException {
File file = new File("c:\\abc.txt");
writeFile(file, "hello");
// delete the file
boolean deleted = file.delete();
System.out.println("Deleted? " + deleted);
}
You open the file, write to it and then do not close it. Java keeps the file open for you, so if you wanted to add more information to it, you could. However, to be able to delete the file, you need to make sure no other reference is open to it. You can do this by using file.close() to close the file handle Java reserves for you.
It's best practice to always close a stream when you are done with it, especially if you added data to it. Otherwise, you might run into situations where you are keepings files open by accident, or, in extreme cases, lose data you thought was saved already.

Have a look at what FileUtils.writeStringToFile() does that you haven't.
public static void writeStringToFile(File file, String data, String encoding) throws IOException {
OutputStream out = new java.io.FileOutputStream(file);
try {
out.write(data.getBytes(encoding));
} finally {
IOUtils.closeQuietly(out);
}
}
You will note that the out stream is always closed, wheras in your example it only gets closed in your catch block if the write() throws an exception.
On Windows, files that are open by any program cannot be deleted.

You just delete your file if an exception occurs. You need to do that every time, after you opened the file.
You may want to put close into a finally block.
If you're using Java 7 I consider using a try-with-ressources block, which takes care of closing files for you.
try (BufferedReader br = new BufferedReader(new FileReader(path)))
{
return br.readLine();
}