This a small part of my code. I want to read the file if it exists. If not, then create a new one. When I restart the program I want to work with the file that is saved. Eclipse says the error is on "ObjectInputStream inStream = new ObjectInputStream(file);" Not sure why.
rooms sbu = new rooms();
File saveFile = new File("SavedObj.obj");
if(saveFile.exists() == false)
{
System.out.println("No save file found. Creating a new file.");
try{
saveFile.createNewFile();
}catch(Exception ex)
{
System.out.println(ex.getMessage());
}
}
else {
FileInputStream file = new FileInputStream(saveFile);
ObjectInputStream inStream = new ObjectInputStream(file);
sbu= (room) inStream.readObject();
}
In the end of my code I store object like this:
FileOutputStream fileOut = new FileOutputStream(saveFile);
ObjectOutputStream outStream = new ObjectOutputStream(fileOut);
outStream.writeObject(sbu);
outStream.close();
isFinished= true;
Any help will be appreciated, thanks a lot!
You can't expect ObjectInputStream to convert text to objects automatically. readObject can only work for the file created by writeObject in ObjectOutputStream.
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import com.pechen.Person;
public class Demo {
public static void main(String [] args) throws Exception{
String filename = "person.obj";
Person person = new Person();
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(filename));
out.writeObject(person);
out.close();
Person p;
ObjectInputStream in = new ObjectInputStream(new FileInputStream(filename));
p = (Person)in.readObject();
in.close();
System.out.println("Read Person: " + p.toString());
}
}
Related
i just need your help. I'm learning java(OOP) and now days we are working on filing. But i got stuck on how to append data in the file. I have written the code and and here's the part of it which is showing the error. Can someone please help me what's wrong with it and why it is not working?
package appending;
import java.io.FileNotFoundException;
import java.util.Formatter;
import java.util.Scanner;
import java.io.FileWriter;
import java.io.BufferedWriter;
public class open {
Formatter output;
public void openFile() throws FileNotFoundException {
output = new Formatter("E:/thisFile.txt");
}
public void addData() {
Scanner input = new Scanner(System.in);
data d = new data();
System.out.println("Enter the data");
d.setData(input.next(),input.nextInt());
output.format("%s","Name and CMS:\t"+d.getData());
FileWriter fileWritter = new FileWriter(File.getPath(),true);
BufferedWriter bufferWritter = new BufferedWriter(fileWritter);
bufferWritter.write(d.getData());
bufferWritter.close();
}
public void close() {
output.close();
}
}
Can try,
public class FileAppend {
public static void main(String[] args) {
PrintWriter out = null;
try{
out = new PrintWriter(new BufferedWriter(new FileWriter("/home/rakesh/myfile.txt", true)));
out.println("appended text");
} catch(Exception e){
e.printStackTrace();
} finally{
out.close();
}
}
}
Creating a text file (note that this will overwrite the file if it already exists):
PrintWriter writer = new PrintWriter("the-file-name.txt", "UTF-8");
writer.println("The first line");
writer.println("The second line");
writer.close();
Creating a binary file (will also overwrite the file):
byte dataToWrite[] = //...
FileOutputStream out = new FileOutputStream("the-file-name");
out.write(dataToWrite);
out.close();
Answer gotten from: How do I create a file and write to it in Java?
If you want to use FileWriter. Try following code:
//FileWriter fw = new FileWriter(new File("path/to/test.txt"), true);
FileWriter fw = new FileWriter("path/to/test.txt", true);
fw.write("This is a sentence");
fw.close();
EDIT You should follow the conventions and capitalize your classes.
I'm trying to develop a simple Java file transfer application using TCP.
My current server code is as follows:
package tcp.ftp;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
public class FTPServer {
public static void main(String[] args) {
new FTPServer().go();
}
void go() {
try {
ServerSocket server = new ServerSocket(2015);
System.out.println("server is running ....!");
while (true) {
Socket socket = server.accept();
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String file = reader.readLine();
System.out.println("file to be downloaded is : " + file);
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));
BufferedOutputStream bos = new BufferedOutputStream(socket.getOutputStream());
while (true) {
int octet = bis.read();
if (octet == -1) {
break;
}
bos.write(octet);
}
bos.flush();
//bos.close();
}
} catch (IOException ex) {
System.out.println(ex.getMessage());
}
}
}
Using my current server code above, the downlloding does not work as expected. the above code sends part of the file to the client , not the entire file. Note that I used the flush method to flush the buffer. but when I replace the flush () method by the close () method, the file is fully sent to the client whithout any loss. Could anyone please explain this behavior!
UPDATE: Here is the code of my client:
package tcp.ftp;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
/**
*
* #author aaa
*/
public class FTPClient {
public static void main(String[] args) {
String file = "JasperReports-Ultimate-Guide-3.pdf";
try {
InetAddress address = InetAddress.getLocalHost();
Socket socket = new Socket(address, 2015);
System.out.println("connection successfully established ....!");
PrintWriter pw = new PrintWriter(socket.getOutputStream());
pw.println(file);
pw.flush();
BufferedInputStream bis = new BufferedInputStream(socket.getInputStream());
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("copy" + file));
while (true) {
int octet = bis.read();
if (octet == -1) {
break;
}
bos.write(octet);
}
bos.flush();
System.out.println("file download is complete ...!");
} catch (UnknownHostException ex) {
System.out.println(ex.getMessage());
} catch (IOException ex) {
System.out.println(ex.getMessage());
}
}
}
Another behavior without the use of Socket. take the following code that copy a file from a source to a destination:
public class CopieFile {
static void fastCopy(String source, String destination) {
try {
FileInputStream fis = new FileInputStream(source);
BufferedInputStream bis = new BufferedInputStream(fis);
FileOutputStream fos = new FileOutputStream(destination);
BufferedOutputStream bos = new BufferedOutputStream(fos);
while (true) {
int octet = bis.read();
if (octet == -1) {
break;
}
bos.write(octet);
}
bos.flush();
} catch (FileNotFoundException ex) {
System.out.println(ex.getMessage());
} catch (IOException ex) {
System.out.println(ex.getMessage());
}
}
public static void main(String[] args) throws IOException {
String source = "...";
String destination = "...";
fastCopy(source, destination);
}// end main
}// end class
the above code to copy a file from one location to another without any loss. Note well that I did not close the stream.
If you never close the stream the client wil never get end of stream so it will never exit the read loop.
In any case the stream and the socket are about to go out of scope, so if you don't close them you have a resource leak.
I am trying to create ".zip" file from byte array but the error given appear everytime I am attempt to open it. Here is the code:
import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.BufferedReader;
import java.io.PrintWriter;
public class ReadTxtFile {
public static void BinFileContToBinArr(String path) throws Throwable{
BufferedReader inputStream = null;
PrintWriter outputStream = null;
try{
String el = null;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
inputStream = new BufferedReader(new FileReader(path));
FileOutputStream fos = new FileOutputStream("D:/texttNE22W.zip");
while((el=inputStream.readLine()) != null){
baos.write(el.getBytes());
}
byte[] b = baos.toByteArray();
for(int i = 0; i<b.length; i++){
System.out.print((char)b[i] + " ");
}
fos.write(b);
}
finally{
if (inputStream!=null){
inputStream.close();
}
if(outputStream!=null){
outputStream.close();
}
}
}
public static void main(String[] args) throws Throwable {
String path = "D:/text.txt";
BinFileContToBinArr(path);
}
}
I've made a research but didn't find a solution. Also, I tried to create a ".txt" file and it works. The only problem is when it comes to creating a ".zip".
Thank you beforehand ! By the way, if someone have encountered this problem before, feel free to vote up or leave me a comment if you wish, because I am interested if it is a common mistake.
You need to use ZipOutputStream instead of FileOutputStream.
I am reading a video file data in bytes and sending to another file but the received video file is not playing properly and is chattered.
Can anyone explain me why this is happening and a solution is appreciated.
My code is as follows
import java.io.*;
public class convert {
public static void main(String[] args) {
//create file object
File file = new File("B:/music/Billa.mp4");
try
{
//create FileInputStream object
FileInputStream fin = new FileInputStream(file);
byte fileContent[] = new byte[(int)file.length()];
fin.read(fileContent);
//create string from byte array
String strFileContent = new String(fileContent);
System.out.println("File content : ");
System.out.println(strFileContent);
File dest=new File("B://music//a.mp4");
BufferedWriter bw=new BufferedWriter(new FileWriter(dest));
bw.write(strFileContent+"\n");
bw.flush();
}
catch(FileNotFoundException e)
{
System.out.println("File not found" + e);
}
catch(IOException ioe)
{
System.out.println("Exception while reading the file " + ioe);
}
}
}
This question might be dead but someone might find this useful.
You can't handle video as string. This is the correct way to read and write (copy) any file using Java 7 or higher.
Please note that size of buffer is processor-dependent and usually should be a power of 2. See this answer for more details.
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
public class FileCopy {
public static void main(String args[]) {
final int BUFFERSIZE = 4 * 1024;
String sourceFilePath = "D:\\MyFolder\\MyVideo.avi";
String outputFilePath = "D:\\OtherFolder\\MyVideo.avi";
try(
FileInputStream fin = new FileInputStream(new File(sourceFilePath));
FileOutputStream fout = new FileOutputStream(new File(outputFilePath));
){
byte[] buffer = new byte[BUFFERSIZE];
while(fin.available() != 0) {
bytesRead = fin.read(buffer);
fout.write(buffer, 0, bytesRead);
}
}
catch(Exception e) {
System.out.println("Something went wrong! Reason: " + e.getMessage());
}
}
}
Hope this also helpful for you - This can read and write a file into another file (You can use any file type to do that)
import java.io.FileInputStream;
import java.io.FileOutputStream;
public class Copy {
public static void main(String[] args) throws Exception {
FileInputStream input = new FileInputStream("input.mp4"); //input file
byte[] data = input.readAllBytes();
FileOutputStream output = new FileOutputStream("output.mp4"); //output file
output.write(data);
output.close();
}
}
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import javax.imageio.ImageIO;
public class Reader {
public Reader() throws Exception{
File file = new File("C:/Users/Digilog/Downloads/Test.mp4");
FileInputStream fin = new FileInputStream(file);
byte b[] = new byte[(int)file.length()];
fin.read(b);
File nf = new File("D:/K.mp4");
FileOutputStream fw = new FileOutputStream(nf);
fw.write(b);
fw.flush();
fw.close();
}
}
In addition to Jakub Orsula's answer, one needs to check the result of read operation to prevent garbage being written to end of file in last iteration.
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
public class FileCopy {
public static void main(String args[]) {
final int BUFFERSIZE = 4 * 1024;
String sourceFilePath = "D:\\MyFolder\\MyVideo.avi";
String outputFilePath = "D:\\OtherFolder\\MyVideo.avi";
try(
FileInputStream fin = new FileInputStream(new File(sourceFilePath));
FileOutputStream fout = new FileOutputStream(new File(outputFilePath));
){
byte[] buffer = new byte[BUFFERSIZE];
int bytesRead;
while(fin.available() != 0) {
bytesRead = fin.read(buffer);
fout.write(buffer, 0, bytesRead);
}
}
catch(Exception e) {
System.out.println("Something went wrong! Reason: " + e.getMessage());
}
}
}
I wrote a code that writes compressed objects into a file, My questions is: is there a way that I could keep track of the increment of size of my file as the object being wrote in? here is my code:
public static void storeCompressedObjs(File outFile, ArrayList<Object[]> obj) {
FileOutputStream fos = null;
GZIPOutputStream gz = null;
ObjectOutputStream oos = null;
try {
fos = new FileOutputStream(outFile);
gz = new GZIPOutputStream(fos);
oos = new ObjectOutputStream(gz);
for (Object str : obj) {
oos.writeObject(str);
oos.flush();
//I was hoping to print outFile.length() here, but it doesn't work
}
} catch (IOException e) {
e.printStackTrace();
} finally {
oos.close();
gz.close();
fos.close();
}
}
I tried to use flush after every oos.writeObject(str); and then get the file size by using outFile.length(), but no matter how much I flush it, the file size remain unchanged until the last jump to its final size. Anyway that I could fix it? Thanks
The Apache Commons project provides a class CountingOutputStream, which you can put into your chain of OutputStreams. You can even have two of them:
package so5997784;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.util.zip.GZIPOutputStream;
import org.apache.commons.io.output.CountingOutputStream;
public class CountBytes {
private static void dump(File outFile, Object... objs) throws IOException {
FileOutputStream fos = new FileOutputStream(outFile);
try {
CountingOutputStream compressedCounter = new CountingOutputStream(fos);
OutputStream gz = new GZIPOutputStream(compressedCounter);
CountingOutputStream uncompressedCounter = new CountingOutputStream(gz);
ObjectOutputStream oos = new ObjectOutputStream(uncompressedCounter);
for (Object obj : objs) {
oos.writeObject(obj);
oos.flush();
System.out.println(uncompressedCounter.getByteCount() + " -> " + compressedCounter.getByteCount());
}
oos.close();
System.out.println(uncompressedCounter.getByteCount() + " -> " + compressedCounter.getByteCount());
} finally {
fos.close();
}
}
public static void main(String[] args) throws IOException {
File outFile = new File("objects.out.gz");
dump(outFile, "a", "b", "cde", "hello", "world");
}
}