Java-J2SE学习笔记

On Windows, this example creates the path \a\b. On Unix, the path would be /a/b. String path = File.separator + "a" + File.separator + "b"; 具有平台独立性 boolean success = (new File("directoryName")).mkdir(); 产生一个目录：注意都是File if (!success) { // Directory creation failed文件夹创建失败 } 产生一个文件 try { File file = new File("filename"); boolean success = file.createNewFile();//返回的是一个boolean型变量 if (success) { // File did not exist and was created } else { // File already exists } } catch (IOException e) { } 产生一个临时文件(只在程序运行时存在) try { // Create temp file. File temp = File.createTempFile("pattern", ".suffix"); // Delete temp file when program exits.程序退出的时候删除 temp.deleteOnExit(); // Write to temp file BufferedWriter out = new BufferedWriter(new FileWriter(temp)); out.write("aString"); out.close(); } catch (IOException e) { } 当前程序工作的目录 String curDir = System.getProperty("user.dir"); System.out.println(curDir); 删除文件夹 // Delete an empty directory boolean success = (new File("directoryName")).delete(); if (!success) { // Deletion failed } 删除文件夹下所有的文件： public static boolean deleteDir(File dir) { if (dir.isDirectory()) { String[] children = dir.list(); for (int i=0; i<children.length; i++) { boolean success = deleteDir(new File(dir, children[i]));//这个地方有一个递归调用 if (!success) { return false; } } } // The directory is now empty so delete it return dir.delete(); } 删除文件： boolean success = (new File("filename")).delete(); if (!success) { // Deletion failed } 查找文件是否存在： boolean exists = (new File("filename")).exists(); if (exists) { // File or directory exists } else { // File or directory does not exist } 路径与URL的转换 // Create a file object File file = new File("filename"); // Convert the file object to a URL URL url = null; try { // The file need not exist. It is made into an absolute path // by prefixing the current working directory url = file.toURL(); //file:/d:/almanac1.4/java.io/filename } catch (MalformedURLException e) { } // Convert the URL to a file object file = new File(url.getFile()); // d:/almanac1.4/java.io/filename // Read the file contents using the URL try { // Open an input stream InputStream is = url.openStream(); // Read from is is.close(); } catch (IOException e) { // Could not open the file } 文件的长度： File file = new File("infilename"); // Get the number of bytes in the file long length = file.length(); 获得文件的父级目录： // Get the parent of a relative filename path File file = new File("Ex1.java"); String parentPath = file.getParent(); // null File parentDir = file.getParentFile(); // null // Get the parents of an absolute filename path file = new File("D:\\almanac\\Ex1.java"); parentPath = file.getParent(); // D:\almanac parentDir = file.getParentFile(); // D:\almanac parentPath = parentDir.getParent(); // D:\ parentDir = parentDir.getParentFile(); // D:\ parentPath = parentDir.getParent(); // null parentDir = parentDir.getParentFile(); // null Related Examples