Develop Reference

How to download a file into the specific folder in java?

I am working on an application which will download 3rd party dependencies to a particular folder and then execute dependency check on it. The files downloaded can be of any type, they can be zip, jar or may b a folder. I am trying to find a code example but nothing seems to work for me. I tried NIO in java but that seems to work only for writing to a particular file not folder. Below is code where I used NIO
// Checking If The File Exists At The Specified Location Or Not
Path filePathObj = Paths.get(filePath);
boolean fileExists = Files.exists(filePathObj);
if(fileExists) {
try {
urlObj = new URL(sampleUrl);
rbcObj = Channels.newChannel(urlObj.openStream());
fOutStream = new FileOutputStream(filePath);
fOutStream.getChannel().transferFrom(rbcObj, 0, Long.MAX_VALUE);
System.out.println("! File Successfully Downloaded From The Url !");
} catch (IOException ioExObj) {
System.out.println("Problem Occured While Downloading The File= " + ioExObj.getMessage());
} finally {
try {
if(fOutStream != null){
fOutStream.close();
}
if(rbcObj != null) {
rbcObj.close();
}
} catch (IOException ioExObj) {
System.out.println("Problem Occured While Closing The Object= " + ioExObj.getMessage());
}
}
} else {
System.out.println("File Not Present! Please Check!");
}```

public Class CopyAndWrite {
public static final String SOURCES = "C:\\Users\\Administrator\\Desktop\\resources";
public static final String TARGET = "C:\\Users\\Administrator\\Desktop\\111";
public static void main (String[]args) throws IOException {
Path startingDir = Paths.get(SOURCES);
Files.walkFileTree(startingDir, new FindJavaVisitor());
}
private static class FindJavaVisitor extends SimpleFileVisitor<Path> {
#Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
if (!StringUtils.equals(dir.toString(), SOURCES)) {
Path targetPath = Paths.get(TARGET + dir.toString().substring(SOURCES.length()));
if (!Files.exists(targetPath)) {
Files.createDirectory(targetPath);
}
}
return FileVisitResult.CONTINUE;
}
#Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
Path targetPath = Paths.get(TARGET + file.toString().substring(SOURCES.length()));
copyFile(targetPath, Files.readAllBytes(file));
return FileVisitResult.CONTINUE;
}
}
private static void copyFile (Path path,byte[] bytes){
// write file
try {
Files.write(path, bytes);
} catch (IOException e) {
e.printStackTrace();
}
}
}

Using OKHttpClient to download the file and place in a folder.
Request request = new Request.Builder().url(downloadUrl).build();
Response response;
try {
response = client.newCall(request).execute();
if (response.isSuccessful()) {
fileName = abc.zip
Path targetPath = new File(inDir + File.separator + fileName).toPath();
try (FileOutputStream fos = new FileOutputStream(targetPath)) {
fos.write(response.body().bytes());
}
return 0;
}
} catch (IOException e) {
logger.error(e.getMessage());
}```

Java hash checking

For some reason i can't figure out why it downloads the new applet every time even though i have the newest application on my computer already (that's what this downloader/checker does, to check the hash, and if its outdated, it re-downloads the newer version which is uploaded to web host)
My downloader class
public class Downloader {
private static final String HASH_URL = "/current";
private static final String DOWNLOAD_URL = ".jar";
private LoadingFrame loadingFrame;
public Downloader(LoadingFrame loadingFrame) {
this.loadingFrame = loadingFrame;
}
private String getLatestHash() {
loadingFrame.setLoadingText("Checking if client is up to date...");
try (InputStream in = new URL(HASH_URL).openStream()) {
return new String(IOUtils.toByteArray(in)).trim();
} catch (IOException e) {
loadingFrame.setLoadingText("Error loading client [ErrorCode: 7A]");
throw new RuntimeException("Error loading client");
}
}
public File downloadLatestPack() {
try {
File dir = new File(System.getProperty("user.home") + File.separator + "Project" + File.separator + "client");
if (!dir.exists()) {
dir.mkdirs();
}
loadingFrame.setLoadingText("Checking if client is up to date...");
String latestHash = getLatestHash();
File latest = new File(dir.getPath() + File.separator + latestHash + ".jar");
if (!latest.exists() || !com.google.common.io.Files.hash(latest, Hashing.sha1()).toString().equals(latestHash)) {
loadingFrame.setLoadingText("Doing some house keeping...");
for (File f : dir.listFiles()) {
if (f.getName().endsWith(".jar") && !f.getName().equals(latest.getName())) {
f.delete();
}
}
loadingFrame.setLoadingText("Downloading latest client...");
latest.createNewFile();
try (InputStream in = new URL(DOWNLOAD_URL).openStream()) {
Files.copy(in, latest.toPath(), StandardCopyOption.REPLACE_EXISTING);
}
} else {
loadingFrame.setLoadingText("Client is up to date!");
}
return latest;
} catch (IOException e) {
loadingFrame.setLoadingText("Error loading client [ErrorCode: 6B]");
throw new RuntimeException("Error loading client");
}
}
}

File Not Found Exception : Open failed:ENOENT

I am new for android, Im downloading image from URL and set in listView. Its working some mobile and not creating file/directory in some mobile.
Its throw error like:
java.io.FileNotFoundException: /storage/emulated/0/.tam/veg.png: open failed: ENOENT (No such file or directory)
I don't know why its throw error like this some mobile. I want to create directory all type of mobile. Please anyone help me.
Here my code:
public class ImageStorage {
public static String saveToSdCard(Bitmap bitmap, String filename) {
String stored = null;
File sdcard = Environment.getExternalStorageDirectory();
File folder = new File(sdcard.getAbsoluteFile(), ".tam");//the dot makes this directory hidden to the user
folder.mkdir();
File file = new File(folder.getAbsoluteFile(), filename) ;
if (file.exists())
return stored ;
try {
FileOutputStream out = new FileOutputStream(file);
bitmap.compress(Bitmap.CompressFormat.PNG, 90, out);
out.flush();
out.close();
stored = "success";
} catch (Exception e) {
e.printStackTrace();
}
return stored;
}
public static File getImage(String imagename) {
File mediaImage = null;
try {
String root = Environment.getExternalStorageDirectory().getAbsolutePath();
File myDir = new File(root);
if (!myDir.exists())
return null;
mediaImage = new File(myDir.getPath() + "/.tam/"+imagename);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return mediaImage;
}
public static File checkifImageExists(String imagename) {
File file = ImageStorage.getImage("/" + imagename);
if (file.exists()) {
return file;
} else {
return null;
}
}
public static String getImageName(String value){
String getName[] = value.split("/");
return getName[4];
}
}
Below path not in all mobile:
/storage/emulated/0/
Thanks in advance!!

Maybe u should check if there's external storage in the mobile before u use this path
public String getDir(Context context) {
String checkPath = null;
if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())
|| !Environment.isExternalStorageRemovable()) {
checkPath = Environment.getExternalStorageDirectory().getPath();
} else {
checkPath = context.getCacheDir().getPath();
}
return checkPath;
}

how to backup file in java?

In reality its just making a copy of a text.txt file. I know how to use file chooser to choose the file but that is as far as my knowledge really goes.
I can do this:
public BasicFile()
{
JFileChooser choose = new JFileChooser(".");
int status = choose.showOpenDialog(null);
try
{
if (status != JFileChooser.APPROVE_OPTION) throw new IOException();
f = choose.getSelectedFile();
if (!f.exists()) throw new FileNotFoundException();
}
catch(FileNotFoundException e)
{
display(1, e.toString(), "File not found ....");
}
catch(IOException e)
{
display(1, e.toString(), "Approve option was not selected");
}
}

Path object is perfect for copying files,
Try this code to copy a file,
Path source = Paths.get("c:\\blabla.txt");
Path target = Paths.get("c:\\blabla2.txt");
try {
Files.copy(source, target);
} catch (IOException e1) {
e1.printStackTrace();
}

If you have to backup a whole folder, you can use this code
public class BackUpFolder {
public void copy(File sourceLocation, File targetLocation) throws IOException {
if (sourceLocation.isDirectory()) {
copyDirectory(sourceLocation, targetLocation);
} else {
copyFile(sourceLocation, targetLocation);
}
}
private void copyDirectory(File source, File target) throws IOException {
if (!target.exists()) {
target.mkdir();
}
for (String f : source.list()) {
copy(new File(source, f), new File(target, f));
}
}
private void copyFile(File source, File target) throws IOException {
try (
InputStream in = new FileInputStream(source);
OutputStream out = new FileOutputStream(target)) {
byte[] buf = new byte[1024];
int length;
while ((length = in.read(buf)) > 0) {
out.write(buf, 0, length);
}
}
}
public static void main(String[] args) {
try {
BackUpFolder backUpFolder = new BackUpFolder();
String location = "./src/edu/abc/locationFiles/daofile"; //File path you are getting from file chooser
String target = "./src"; //target place you want to patse
File locFile = new File(location);
File tarFile = new File(target);
backUpFolder.copyDirectory(locFile, tarFile);
} catch (IOException ex) {
Logger.getLogger(BackUpFolder.class.getName()).log(Level.SEVERE, null, ex);
}
}
}

Start by taking a look at Basic I/O, which explains the basics of Input/OutputStreams and Readers and Writers, which are used to read/write bytes of data from a source to a destination.
If you're using Java 7 or over, you should also take a look at Copying a File or Directory which is part of newer Files and Paths API, which you can find more information about at File I/O (Featuring NIO.2)

How to copy file from one location to another location?

I want to copy a file from one location to another location in Java. What is the best way to do this?
Here is what I have so far:
import java.io.File;
import java.io.FilenameFilter;
import java.util.ArrayList;
import java.util.List;
public class TestArrayList {
public static void main(String[] args) {
File f = new File(
"D:\\CBSE_Demo\\Demo_original\\fscommand\\contentplayer\\config");
List<String>temp=new ArrayList<String>();
temp.add(0, "N33");
temp.add(1, "N1417");
temp.add(2, "N331");
File[] matchingFiles = null;
for(final String temp1: temp){
matchingFiles = f.listFiles(new FilenameFilter() {
public boolean accept(File dir, String name) {
return name.startsWith(temp1);
}
});
System.out.println("size>>--"+matchingFiles.length);
}
}
}
This does not copy the file, what is the best way to do this?

You can use this (or any variant):
Files.copy(src, dst, StandardCopyOption.REPLACE_EXISTING);
Also, I'd recommend using File.separator or / instead of \\ to make it compliant across multiple OS, question/answer on this available here.
Since you're not sure how to temporarily store files, take a look at ArrayList:
List<File> files = new ArrayList();
files.add(foundFile);
To move a List of files into a single directory:
List<File> files = ...;
String path = "C:/destination/";
for(File file : files) {
Files.copy(file.toPath(),
(new File(path + file.getName())).toPath(),
StandardCopyOption.REPLACE_EXISTING);
}

Update:
see also
https://stackoverflow.com/a/67179064/1847899
Using Stream
private static void copyFileUsingStream(File source, File dest) throws IOException {
InputStream is = null;
OutputStream os = null;
try {
is = new FileInputStream(source);
os = new FileOutputStream(dest);
byte[] buffer = new byte[1024];
int length;
while ((length = is.read(buffer)) > 0) {
os.write(buffer, 0, length);
}
} finally {
is.close();
os.close();
}
}
Using Channel
private static void copyFileUsingChannel(File source, File dest) throws IOException {
FileChannel sourceChannel = null;
FileChannel destChannel = null;
try {
sourceChannel = new FileInputStream(source).getChannel();
destChannel = new FileOutputStream(dest).getChannel();
destChannel.transferFrom(sourceChannel, 0, sourceChannel.size());
}finally{
sourceChannel.close();
destChannel.close();
}
}
Using Apache Commons IO lib:
private static void copyFileUsingApacheCommonsIO(File source, File dest) throws IOException {
FileUtils.copyFile(source, dest);
}
Using Java SE 7 Files class:
private static void copyFileUsingJava7Files(File source, File dest) throws IOException {
Files.copy(source.toPath(), dest.toPath());
}
Or try Googles Guava :
https://github.com/google/guava
docs:
https://guava.dev/releases/snapshot-jre/api/docs/com/google/common/io/Files.html

Use the New Java File classes in Java >=7.
Create the below method and import the necessary libs.
public static void copyFile( File from, File to ) throws IOException {
Files.copy( from.toPath(), to.toPath() );
}
Use the created method as below within main:
File dirFrom = new File(fileFrom);
File dirTo = new File(fileTo);
try {
copyFile(dirFrom, dirTo);
} catch (IOException ex) {
Logger.getLogger(TestJava8.class.getName()).log(Level.SEVERE, null, ex);
}
NB:- fileFrom is the file that you want to copy to a new file fileTo in a different folder.
Credits - #Scott: Standard concise way to copy a file in Java?

public static void copyFile(File oldLocation, File newLocation) throws IOException {
if ( oldLocation.exists( )) {
BufferedInputStream reader = new BufferedInputStream( new FileInputStream(oldLocation) );
BufferedOutputStream writer = new BufferedOutputStream( new FileOutputStream(newLocation, false));
try {
byte[] buff = new byte[8192];
int numChars;
while ( (numChars = reader.read( buff, 0, buff.length ) ) != -1) {
writer.write( buff, 0, numChars );
}
} catch( IOException ex ) {
throw new IOException("IOException when transferring " + oldLocation.getPath() + " to " + newLocation.getPath());
} finally {
try {
if ( reader != null ){
writer.close();
reader.close();
}
} catch( IOException ex ){
Log.e(TAG, "Error closing files when transferring " + oldLocation.getPath() + " to " + newLocation.getPath() );
}
}
} else {
throw new IOException("Old location does not exist when transferring " + oldLocation.getPath() + " to " + newLocation.getPath() );
}
}

Copy a file from one location to another location means,need to copy the whole content to another location.Files.copy(Path source, Path target, CopyOption... options) throws IOException this method expects source location which is original file location and target location which is a new folder location with destination same type file(as original).
Either Target location needs to exist in our system otherwise we need to create a folder location and then in that folder location we need to create a file with the same name as original filename.Then using copy function we can easily copy a file from one location to other.
public static void main(String[] args) throws IOException {
String destFolderPath = "D:/TestFile/abc";
String fileName = "pqr.xlsx";
String sourceFilePath= "D:/TestFile/xyz.xlsx";
File f = new File(destFolderPath);
if(f.mkdir()){
System.out.println("Directory created!!!!");
}
else {
System.out.println("Directory Exists!!!!");
}
f= new File(destFolderPath,fileName);
if(f.createNewFile()) {
System.out.println("File Created!!!!");
} else {
System.out.println("File exists!!!!");
}
Files.copy(Paths.get(sourceFilePath), Paths.get(destFolderPath, fileName),REPLACE_EXISTING);
System.out.println("Copy done!!!!!!!!!!!!!!");
}

You can do it with the Java 8 Streaming API, PrintWriter and the Files API
try (PrintWriter pw = new PrintWriter(new File("destination-path"), StandardCharsets.UTF_8)) {
Files.readAllLines(Path.of("src/test/resources/source-file.something"), StandardCharsets.UTF_8)
.forEach(pw::println);
}
If you want to modify the content on-the-fly while copying, check out this link for the extended example https://overflowed.dev/blog/copy-file-and-modify-with-java-streams/

I modified one of the answers to make it a bit more efficient.
public void copy(){
InputStream in = null;
try {
in = new FileInputStream(Files);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
try {
OutputStream out = new FileOutputStream();
try {
// Transfer bytes from in to out
byte[] buf = new byte[1024];
while (true) {
int len = 0;
try {
if (!((len = in.read(buf)) > 0)) break;
} catch (IOException e) {
e.printStackTrace();
}
try {
out.write(buf, 0, len);
} catch (IOException e) {
e.printStackTrace();
}
}
} finally {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
} finally {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void moveFile() {
copy();
File dir = getFilesDir();
File file = new File(dir, "my_filename");
boolean deleted = file.delete();
}

Files.exists()
Files.createDirectory()
Files.copy()
Overwriting Existing Files:
Files.move()
Files.delete()
Files.walkFileTree()
enter link description here

You can use
FileUtils.copy(sourceFile, destinationFile);
https://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/FileUtils.html