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'