Seven ways to copy files in java

Article directory

• 1. Copy files by byte stream
• 2. File copy through character stream
• 3. File copy through byte buffer stream
• 4. Copy files through character buffer stream
• 5. Copy files through JAVA NIO indirect buffer
• 6. Copy files through JAVA NIO direct buffer
• 7. Transfer copy files through JAVA NIO channel
• Use example

/** * Copy files by byte stream * @param sourcePath Source file path * @param targetPath Destination file path */ public static void copyFileByStream(String sourcePath,String targetPath){ //Source file path File source = new File(sourcePath); //Destination file path File target = new File(targetPath); //Cannot copy if source file does not exist if(!source.exists()){ return; } //Create if the destination file directory does not exist if(!target.getParentFile().exists()){ target.getParentFile().mkdirs(); } try { //Copy files InputStream inputStream = new FileInputStream(source); OutputStream outputStream = new FileOutputStream(target); int temp = 0; //Read 1024 bytes at a time byte[] data = new byte[1024]; //Save the data read each time to the byte array, and return the number of reads while ((temp = inputStream.read(data)) != -1){ //Output array outputStream.write(data,0,temp); } inputStream.close(); outputStream.close(); } catch (IOException e) { e.printStackTrace(); } }

Only text files can be copied using character streams

/** * Copy files by character stream * * @param sourcePath Source file path * @param targetPath Destination file path */ public static void copyFileByReaderAndWriter(String sourcePath, String targetPath) { //Source file path File source = new File(sourcePath); //Destination file path File target = new File(targetPath); //Cannot copy if source file does not exist if (!source.exists()) { return; } //Create if the destination file directory does not exist if (!target.getParentFile().exists()) { target.getParentFile().mkdirs(); } FileReader in = null; FileWriter out = null; try { //Character input stream and character output stream in = new FileReader(source); out = new FileWriter(target); char[] c = new char[1024]; int temp = 0; //1024 characters at a time while ((temp = in.read(c)) != -1) { //output to a file out.write(c, 0, temp); } } catch (IOException e) { e.printStackTrace(); } finally { //Closed flow try { if (in != null) { in.close(); } if (out != null) { out.close(); } } catch (IOException e) { e.printStackTrace(); } } }

/** * Copy files by byte buffer stream * * @param sourcePath Source file path * @param targetPath Destination file path */ public static void copyFileByBuffered(String sourcePath, String targetPath){ //Source file path File source = new File(sourcePath); //Destination file path File target = new File(targetPath); //Cannot copy if source file does not exist if (!source.exists()) { return; } //Create if the destination file directory does not exist if (!target.getParentFile().exists()) { target.getParentFile().mkdirs(); } InputStream in = null; OutputStream out = null; try { //Byte buffered input stream and byte buffered output stream in = new BufferedInputStream(new FileInputStream(source)); out = new BufferedOutputStream(new FileOutputStream(target)); byte[] b = new byte[1024]; int temp = 0; //Read a byte array of 1024 at a time while((temp = in.read(b)) != -1){ //output to a file out.write(b,0,temp); } } catch (Exception e) { e.printStackTrace(); }finally { //Closed flow try { if (in != null) { in.close(); } if (out != null) { out.close(); } } catch (IOException e) { e.printStackTrace(); } } }

Character buffer streams can only read text files

/** * Copy files by character buffer stream * * @param sourcePath Source file path * @param targetPath Destination file path */ public static void copyFileByBufferedChar(String sourcePath, String targetPath){ //Source file path File source = new File(sourcePath); //Destination file path File target = new File(targetPath); //Cannot copy if source file does not exist if (!source.exists()) { return; } //Create if the destination file directory does not exist if (!target.getParentFile().exists()) { target.getParentFile().mkdirs(); } BufferedReader in = null; BufferedWriter out = null; try { //Character buffered input stream and character buffered output stream in = new BufferedReader(new FileReader(source)); out = new BufferedWriter(new FileWriter(target)); //Read file (one line at a time) String temp = null; while((temp = in.readLine()) != null){ //output to a file out.write(temp); } } catch (Exception e) { e.printStackTrace(); }finally { //Closed flow try { if (in != null) { in.close(); } if (out != null) { out.close(); } } catch (IOException e) { e.printStackTrace(); } } }

/** * Copying files through JAVA NIO indirect buffer * * @param sourcePath Source file path * @param targetPath Destination file path */ public static void copyFileByChannel(String sourcePath, String targetPath) { FileChannel outChannel = null; FileChannel inChannel = null; FileInputStream fis = null; FileOutputStream fos = null; try { fis = new FileInputStream(sourcePath); fos = new FileOutputStream(targetPath); //Access channel inChannel = fis.getChannel(); outChannel = fos.getChannel(); //Allocate buffer of specified size ByteBuffer buf = ByteBuffer.allocate(1024); while (inChannel.read(buf) != -1) { //Convert to read data mode buf.flip(); //Write to disk outChannel.write(buf); //Clear buffer buf.clear(); } } catch (Exception e) { e.printStackTrace(); } finally { //Closed flow try { if (outChannel != null) { outChannel.close(); } if (inChannel != null) { inChannel.close(); } if (fis != null) { fis.close(); } if (fos != null) { fos.close(); } } catch (IOException e) { e.printStackTrace(); } } }

/** * Copying files (memory mapping files) through JAVA NIO direct buffer * * @param sourcePath Source file path * @param targetPath Destination file path */ public static void copyFileByChannelBufferd(String sourcePath, String targetPath) { FileChannel inChannel = null; FileChannel outChannel = null; try { //Get channel, StandardOpenOption.READ means readable, StandardOpenOption.WRITE means writable, StandardOpenOption.CREATE means can be created inChannel = FileChannel.open(Paths.get(sourcePath), StandardOpenOption.READ); outChannel = FileChannel.open(Paths.get(targetPath), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE); //Create memory map file MappedByteBuffer inMapped = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size()); MappedByteBuffer outMapped = outChannel.map(FileChannel.MapMode.READ_WRITE, 0, inChannel.size()); //Direct operation memory mapping file byte[] buf = new byte[inMapped.limit()]; inMapped.get(buf); outMapped.put(buf); } catch (IOException e) { e.printStackTrace(); } finally { //Closed flow try { if (outChannel != null) { outChannel.close(); } if (inChannel != null) { inChannel.close(); } } catch (IOException e) { e.printStackTrace(); } } }

One way

/** * Transfer copy files through JAVA NIO channel * * @param sourcePath Source file path * @param targetPath Destination file path */ public static void copyFileByChannelTransfer(String sourcePath, String targetPath) { FileChannel inChannel = null; FileChannel outChannel = null; try { //Access channel inChannel = FileChannel.open(Paths.get(sourcePath), StandardOpenOption.READ); outChannel = FileChannel.open(Paths.get(targetPath),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE); inChannel.transferTo(0,inChannel.size(),outChannel); } catch (IOException e) { e.printStackTrace(); }finally { //Closed flow try { if (outChannel != null) { outChannel.close(); } if (inChannel != null) { inChannel.close(); } } catch (IOException e) { e.printStackTrace(); } } }

Mode two

/** * Transfer copy files through JAVA NIO channel * * @param sourcePath Source file path * @param targetPath Destination file path */ public static void copyFileByChannelTransfer2(String sourcePath, String targetPath) { FileInputStream fis = null; FileOutputStream fos = null; FileChannel inChannel = null; FileChannel outChannel = null; try { fis = new FileInputStream(sourcePath); fos = new FileOutputStream(targetPath); //Access channel inChannel = fis.getChannel(); outChannel = fos.getChannel(); inChannel.transferTo(0,inChannel.size(),outChannel); } catch (IOException e) { e.printStackTrace(); }finally { //Closed flow try { if (outChannel != null) { outChannel.close(); } if (inChannel != null) { inChannel.close(); } } catch (IOException e) { e.printStackTrace(); } } }

String source = "e:\\demo\\Emperor of heaven.txt"; String target = "e:\\demo\\; long time1 = System.currentTimeMillis(); copyFileByStream(source

3 February 2020, 09:17 | Views: 6088

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