操作方法
预处理文件。这里有三种格式的源文件。包括 1. 占用空间117M，大小70.1M的21471个小文件组成的文件夹 2. 上述小文件通过zip格式压缩后形成的zip文件，大小33.9M 3. 上述小文件写在一个文件中后的一个大文件70.3M（每个文件占用两行，第一行为文件名，第二行为文件内容）
分别通过默认的带有Buffer的字节输入流与字符输入流来读取三种格式的文件。（缓冲区使用默认的8k，参考资料中说明了8k是一个综合效果较好的缓冲区大小）。代码在下一个“代码”部分。
下面是结果示例，可以看到 1. 字节流明显比字符流有更快的速度，只是有时候可能需要使用字符流来方便进行人机交互。 2. 小文件由于打开IO频繁，其效率是最慢的 3. 带有Buffer的大文件是其中速度最快的，但是由于将多个文件组合在一个文件中，这个就需要自己设置分割方式，以及区分的办法了 4. zip文件居中 5. 在本次实验中对于字节流的读写，速度大概是1:10:100的比例 对于字符流的速度大约是1:4:20的样子
代码
三种格式文件读取代码： public static File[] get()//读取一个大文件 { return new File[]{new File("C:/Users/Administrator/Desktop/文件存取/zh_en.txt")}; } public static File [] get()//读取多个小文件 { return new File("C:/Users/Administrator/Desktop/文件存取/zh_en").listFiles(); } public static ZipInputStream get() throws IOException//读取zip文件 { return new ZipInputStream(new BufferedInputStream(new FileInputStream(new File("C:/Users/Administrator/Desktop/文件存取/zh_en.zip")))); }
zip文件测试 public static void main(String[] args) throws IOException { System.out.println("StrTime\t" + Time()); System.out.println("StreamTime\t" + Time2()); } private static long Time() throws IOException { ZipInputStream zis = GiveFiles.get(); long start = System.currentTimeMillis(); int all = 0; ZipEntry entry; BufferedReader br = new BufferedReader(new InputStreamReader(zis)); while ((entry = zis.getNextEntry()) != null) { if(!entry.isDirectory()) { String line = ""; while((line = br.readLine()) != null) { all += line.length(); } } zis.closeEntry(); } br.close(); zis.close(); System.out.println(all); return System.currentTimeMillis() - start; } private static long Time2() throws IOException { ZipInputStream zis = GiveFiles.get(); long start = System.currentTimeMillis(); int all = 0; ZipEntry entry; while ((entry = zis.getNextEntry()) != null) { if(!entry.isDirectory()) { byte [] temp = new byte[1024]; int length = 0; while((length = zis.read(temp)) > 0) { all += length; } } zis.closeEntry(); } zis.close(); System.out.println(all); return System.currentTimeMillis() - start; }
多个小文件测试 public static void main(String[] args) throws IOException { System.out.println("StreamIOFilesTime\t" + StreamIOFilesTime()); System.out.println("StrIOFilesTime\t" + StrIOFilesTime()); System.out.println("RandomIOFilesTime\t" + RandomIOFilesTime()); } private static long RandomIOFilesTime() throws IOException { File [] files = GiveFiles.get(); long start = System.currentTimeMillis(); int all = 0; for (File file : files) { byte [] temp = new byte[1024]; int length = 0; RandomAccessFile rfile = new RandomAccessFile(file, "r"); while((length = rfile.read(temp)) > 0) { all += length; } rfile.close(); } System.out.println(all); return System.currentTimeMillis() - start; } private static long StreamIOFilesTime() throws IOException { File [] files = GiveFiles.get(); long start = System.currentTimeMillis(); int all = 0; for (File file : files) { int length = 0; BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file)); byte [] temp = new byte[1024]; while((length = bis.read(temp)) > 0) { all += length; } bis.close(); } System.out.println(all); return System.currentTimeMillis() - start; } private static long StrIOFilesTime() throws IOException { File [] files = GiveFiles.get(); long start = System.currentTimeMillis(); int all = 0; for (File file : files) { BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file))); String temp = ""; while((temp = br.readLine()) != null) { all += temp.length(); } br.close(); } System.out.println(all); return System.currentTimeMillis() - start; }
大文件测试 public static void main(String[] args) throws IOException { System.out.println("StreamIOFilesTime\t" + StreamIOFilesTime()); System.out.println("StrIOFilesTime\t" + StrIOFilesTime()); System.out.println("RandomIOFilesTime\t" + RandomIOFilesTime()); } private static long RandomIOFilesTime() throws IOException { File [] files = GiveFiles.get(); long start = System.currentTimeMillis(); int all = 0; for (File file : files) { byte [] temp = new byte[1024]; int length = 0; RandomAccessFile rfile = new RandomAccessFile(file, "r"); while((length = rfile.read(temp)) > 0) { all += length; } rfile.close(); } System.out.println(all); return System.currentTimeMillis() - start; } private static long StreamIOFilesTime() throws IOException { File [] files = GiveFiles.get(); long start = System.currentTimeMillis(); int all = 0; for (File file : files) { int length = 0; BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file)); byte [] temp = new byte[1024]; while((length = bis.read(temp)) > 0) { all += length; } bis.close(); } System.out.println(all); return System.currentTimeMillis() - start; } private static long StrIOFilesTime() throws IOException { File [] files = GiveFiles.get(); long start = System.currentTimeMillis(); int all = 0; for (File file : files) { BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file))); String temp = ""; while((temp = br.readLine()) != null) { all += temp.length(); } br.close(); } System.out.println(all); return System.currentTimeMillis() - start; }