壓縮20M文件從30秒到1秒的優(yōu)化過程

public static void zipFileNoBuffer() {    File zipFile = new File(ZIP_FILE);    try (ZipOutputStream zipOut = new ZipOutputStream(new FileOutputStream(zipFile))) {        //開始時間        long beginTime = System.currentTimeMillis();
        for (int i = 0; i < 10; i++) {            try (InputStream input = new FileInputStream(JPG_FILE)) {                zipOut.putNextEntry(new ZipEntry(FILE_NAME + i));                int temp = 0;                while ((temp = input.read()) != -1) {                    zipOut.write(temp);                }            }        }        printInfo(beginTime);    } catch (Exception e) {        e.printStackTrace();    }}

fileSize:20Mconsum?time:29599

/** * Reads a byte of data from this input stream. This method blocks * if no input is yet available. * * @return     the next byte of data, or -1 if the end of the *             file is reached. * @exception  IOException  if an I/O error occurs. */public?native?int?read()?throws?IOException;

public static void zipFileBuffer() {    File zipFile = new File(ZIP_FILE);    try (ZipOutputStream zipOut = new ZipOutputStream(new FileOutputStream(zipFile));            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(zipOut)) {        //開始時間        long beginTime = System.currentTimeMillis();        for (int i = 0; i < 10; i++) {            try (BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(JPG_FILE))) {                zipOut.putNextEntry(new ZipEntry(FILE_NAME + i));                int temp = 0;                while ((temp = bufferedInputStream.read()) != -1) {                    bufferedOutputStream.write(temp);                }            }        }        printInfo(beginTime);    } catch (Exception e) {        e.printStackTrace();    }}

------BufferfileSize:20Mconsum?time:1808

public static void zipFileChannel() {    //開始時間    long beginTime = System.currentTimeMillis();    File zipFile = new File(ZIP_FILE);    try (ZipOutputStream zipOut = new ZipOutputStream(new FileOutputStream(zipFile));            WritableByteChannel writableByteChannel = Channels.newChannel(zipOut)) {        for (int i = 0; i < 10; i++) {            try (FileChannel fileChannel = new FileInputStream(JPG_FILE).getChannel()) {                zipOut.putNextEntry(new ZipEntry(i + SUFFIX_FILE));                fileChannel.transferTo(0, FILE_SIZE, writableByteChannel);            }        }        printInfo(beginTime);    } catch (Exception e) {        e.printStackTrace();    }}

This method is potentially much more efficient than a simple loop* that reads from this channel and writes to the target channel.  Many* operating systems can transfer bytes directly from the filesystem cache*?to?the?target?channel?without?actually?copying?them.?

------ChannelfileSize:20Mconsum?time:1416

//Version 4 使用Map映射文件public static void zipFileMap() {    //開始時間    long beginTime = System.currentTimeMillis();    File zipFile = new File(ZIP_FILE);    try (ZipOutputStream zipOut = new ZipOutputStream(new FileOutputStream(zipFile));            WritableByteChannel writableByteChannel = Channels.newChannel(zipOut)) {        for (int i = 0; i < 10; i++) {
            zipOut.putNextEntry(new ZipEntry(i + SUFFIX_FILE));
            //內(nèi)存中的映射文件            MappedByteBuffer mappedByteBuffer = new RandomAccessFile(JPG_FILE_PATH, "r").getChannel()                    .map(FileChannel.MapMode.READ_ONLY, 0, FILE_SIZE);
            writableByteChannel.write(mappedByteBuffer);        }        printInfo(beginTime);    } catch (Exception e) {        e.printStackTrace();    }}

---------MapfileSize:20Mconsum?time:1305

 Whether or not a thread writing bytes to a pipe will block until another?thread?reads?those?bytes

//Version 5 使用Pippublic?static?void?zipFilePip()?{    long beginTime = System.currentTimeMillis();    try(WritableByteChannel out = Channels.newChannel(new FileOutputStream(ZIP_FILE))) {        Pipe pipe = Pipe.open();        //異步任務(wù)        CompletableFuture.runAsync(()->runTask(pipe));
        //獲取讀通道        ReadableByteChannel readableByteChannel = pipe.source();        ByteBuffer buffer = ByteBuffer.allocate(((int) FILE_SIZE)*10);        while (readableByteChannel.read(buffer)>= 0) {            buffer.flip();            out.write(buffer);            buffer.clear();        }    }catch (Exception e){        e.printStackTrace();    }????printInfo(beginTime);}
//異步任務(wù)public?static?void?runTask(Pipe?pipe)?{    try(ZipOutputStream zos = new ZipOutputStream(Channels.newOutputStream(pipe.sink()));            WritableByteChannel out = Channels.newChannel(zos)) {        System.out.println("Begin");        for (int i = 0; i < 10; i++) {????????????zos.putNextEntry(new?ZipEntry(i+SUFFIX_FILE));????????????FileChannel?jpgChannel?=?new?FileInputStream(new?File(JPG_FILE_PATH)).getChannel();????????????jpgChannel.transferTo(0,?FILE_SIZE,?out);            jpgChannel.close();        }    }catch (Exception e){        e.printStackTrace();    }}