zip压缩文件（二）

普通压缩文件以20M大小的文件为例

   public static void main(String[] args) {

        String source = "F:\\demo\\择天记 第5季 第01话 标清(270P).qlv";

        String zipFile = "F:\\demo\\zip\\择天记.zip";

        zipFileNoBuffer(zipFile, source);

    }

    public static void zipFileNoBuffer(String zipFilePath, String sourceFilePath) {

        try {

            File zipFile = new File(zipFilePath);

            File sourceFile = new File(sourceFilePath);

            long length = sourceFile.length();

            System.out.println("开始压缩文件、文件大小:[" + formetFileSize(length) + "] ...");

            long beginTime = System.currentTimeMillis();

            ZipOutputStream zipOut = new ZipOutputStream(new FileOutputStream(zipFile));

            InputStream input = new FileInputStream(sourceFile);

            zipOut.putNextEntry(new ZipEntry(sourceFile.getName()));

            int temp = 0;

            while ((temp = input.read()) != -1) {

                zipOut.write(temp);

            }

            input.close();

            zipOut.closeEntry();

            zipOut.close();

            //时间耗时

            System.out.println("压缩完毕,耗时：[" + printTimeConsuming(beginTime) + "] ms ...");

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

结果：

Connected to the target VM, address: '127.0.0.1:49281', transport: 'socket'

开始压缩文件、文件大小:[21.24M] ...

压缩完毕,耗时：[68652] ms ...

Disconnected from the target VM, address: '127.0.0.1:49281', transport: 'socket'

利用缓冲区BufferInputStream 优化

   private static void firstZipFile(String zipFilePath, String sourceFilePath){

         try {

             File zipFile = new File(zipFilePath);

             File sourceFile = new File(sourceFilePath);

             long length = sourceFile.length();

             System.out.println("开始压缩文件、文件大小:[" + formetFileSize(length) + "] ...");

             long beginTime = System.currentTimeMillis();

             FileOutputStream fileOut = new FileOutputStream(zipFile);

             ZipOutputStream zipOut = new ZipOutputStream(fileOut);

             BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(zipOut);

             InputStream input = new FileInputStream(sourceFile);

             BufferedInputStream bufferedInputStream = new BufferedInputStream(input);

             zipOut.putNextEntry(new ZipEntry(sourceFile.getName()));

             int temp = 0;

             while ((temp = bufferedInputStream.read()) != -1) {

                 bufferedOutputStream.write(temp);

             }

             bufferedInputStream.close();

             input.close();

             bufferedOutputStream.close();

             zipOut.close();

             fileOut.close();

             //时间耗时

             System.out.println("压缩完毕,耗时：[" + printTimeConsuming(beginTime) + "] ms ...");

         } catch (Exception e) {

             e.printStackTrace();

         }

     }

结果：耗时缩短了（68652-2501）毫秒

Connected to the target VM, address: '127.0.0.1:51524', transport: 'socket'

开始压缩文件、文件大小:[21.24M] ...

压缩完毕,耗时：[2501] ms ...

Disconnected from the target VM, address: '127.0.0.1:51524', transport: 'socket'

　说明：

这是一个调用本地方法与原生操作系统进行交互，从磁盘中读取数据。每读取一个字节的数据就调用一次本地方法与操作系统交互，是非常耗时的。例如我们现在有30000个字节的数据，如果使用FileInputStream那么就需要调用30000次的本地方法来获取这些数据，而如果使用缓冲区的话（这里假设初始的缓冲区大小足够放下30000字节的数据）那么只需要调用一次就行。因为缓冲区在第一次调用read()方法的时候会直接从磁盘中将数据直接读取到内存中。随后再一个字节一个字节的慢慢返回。

第二次优化：

 /**

      * 第二次优化使用 Channel

      */

     private static void secondZipFile(String zipFilePath, String sourceFilePath ){

         try {

             File zipFile = new File(zipFilePath);

             File sourceFile = new File(sourceFilePath);

             long length = sourceFile.length();

             System.out.println("开始压缩文件、文件大小:[" + formetFileSize(length) + "] ...");

             long beginTime = System.currentTimeMillis();

             FileOutputStream fileOut = new FileOutputStream(zipFile);

             ZipOutputStream zipOut = new ZipOutputStream(fileOut);

             WritableByteChannel writableByteChannel = Channels.newChannel(zipOut);

             FileInputStream input = new FileInputStream(sourceFile);

             FileChannel channel =  input.getChannel();

             zipOut.putNextEntry(new ZipEntry(sourceFile.getName()));

             channel.transferTo(0, length, writableByteChannel);

             channel.close();

             input.close();

             writableByteChannel.close();

             zipOut.close();

             fileOut.close();

             //时间耗时

             System.out.println("压缩完毕,耗时：[" + printTimeConsuming(beginTime) + "] ms ...");

         } catch (Exception e) {

             e.printStackTrace();

         }

     }

结果：比第一次优化耗时缩短了（2501-1810）毫秒

Connected to the target VM, address: '127.0.0.1:52021', transport: 'socket'

开始压缩文件、文件大小:[21.24M] ...

压缩完毕,耗时：[1810] ms ...

Disconnected from the target VM, address: '127.0.0.1:52021', transport: 'socket'

巴特西

zip压缩文件（二）

最新文章

热门文章