zip压缩文件（二）
作者：互联网
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
1 private static void firstZipFile(String zipFilePath, String sourceFilePath){
2 try {
3 File zipFile = new File(zipFilePath);
4 File sourceFile = new File(sourceFilePath);
5 long length = sourceFile.length();
6 System.out.println("开始压缩文件、文件大小:[" + formetFileSize(length) + "] ...");
7 long beginTime = System.currentTimeMillis();
8 FileOutputStream fileOut = new FileOutputStream(zipFile);
9 ZipOutputStream zipOut = new ZipOutputStream(fileOut);
10 BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(zipOut);
11 InputStream input = new FileInputStream(sourceFile);
12 BufferedInputStream bufferedInputStream = new BufferedInputStream(input);
13 zipOut.putNextEntry(new ZipEntry(sourceFile.getName()));
14 int temp = 0;
15 while ((temp = bufferedInputStream.read()) != -1) {
16 bufferedOutputStream.write(temp);
17 }
18 bufferedInputStream.close();
19 input.close();
20 bufferedOutputStream.close();
21 zipOut.close();
22 fileOut.close();
23 //时间耗时
24 System.out.println("压缩完毕,耗时：[" + printTimeConsuming(beginTime) + "] ms ...");
25 } catch (Exception e) {
26 e.printStackTrace();
27 }
28 }
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：
1 /**
2 * 第二次优化使用 Channel
3 */
4 private static void secondZipFile(String zipFilePath, String sourceFilePath ){
5 try {
6 File zipFile = new File(zipFilePath);
7 File sourceFile = new File(sourceFilePath);
8 long length = sourceFile.length();
9 System.out.println("开始压缩文件、文件大小:[" + formetFileSize(length) + "] ...");
10 long beginTime = System.currentTimeMillis();
11 FileOutputStream fileOut = new FileOutputStream(zipFile);
12 ZipOutputStream zipOut = new ZipOutputStream(fileOut);
13 WritableByteChannel writableByteChannel = Channels.newChannel(zipOut);
14 FileInputStream input = new FileInputStream(sourceFile);
15 FileChannel channel = input.getChannel();
16 zipOut.putNextEntry(new ZipEntry(sourceFile.getName()));
17 channel.transferTo(0, length, writableByteChannel);
18 channel.close();
19 input.close();
20 writableByteChannel.close();
21 zipOut.close();
22 fileOut.close();
23 //时间耗时
24 System.out.println("压缩完毕,耗时：[" + printTimeConsuming(beginTime) + "] ms ...");
25 } catch (Exception e) {
26 e.printStackTrace();
27 }
28 }
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'
标签：...,zip,sourceFile,zipOut,压缩文件,File,close,new 来源： https://www.cnblogs.com/lxn0216/p/12509721.html