Java File类总结和FileUtils类

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package com.mengdd.file;import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;/** FileUtils copied from org.apache.commons.io.FileUtils*/
public class FileUtils {/*** Construct a file from the set of name elements.** @param directory*            the parent directory* @param names*            the name elements* @return the file*/public static File getFile(File directory, String... names) {if (directory == null) {throw new NullPointerException("directorydirectory must not be null");}if (names == null) {throw new NullPointerException("names must not be null");}File file = directory;for (String name : names) {file = new File(file, name);}return file;}/*** Construct a file from the set of name elements.** @param names*            the name elements* @return the file*/public static File getFile(String... names) {if (names == null) {throw new NullPointerException("names must not be null");}File file = null;for (String name : names) {if (file == null) {file = new File(name);}else {file = new File(file, name);}}return file;}/*** Opens a {@link FileInputStream} for the specified file, providing better* error messages than simply calling <code>new FileInputStream(file)</code>* .* <p>* At the end of the method either the stream will be successfully opened,* or an exception will have been thrown.* <p>* An exception is thrown if the file does not exist. An exception is thrown* if the file object exists but is a directory. An exception is thrown if* the file exists but cannot be read.** @param file*            the file to open for input, must not be {@code null}* @return a new {@link FileInputStream} for the specified file* @throws FileNotFoundException*             if the file does not exist* @throws IOException*             if the file object is a directory* @throws IOException*             if the file cannot be read*/public static FileInputStream openInputStream(File file) throws IOException {if (file.exists()) {if (file.isDirectory()) {throw new IOException("File '" + file+ "' exists but is a directory");}if (file.canRead() == false) {throw new IOException("File '" + file + "' cannot be read");}}else {throw new FileNotFoundException("File '" + file+ "' does not exist");}return new FileInputStream(file);}/*** Opens a {@link FileOutputStream} for the specified file, checking and* creating the parent directory if it does not exist.* <p>* At the end of the method either the stream will be successfully opened,* or an exception will have been thrown.* <p>* The parent directory will be created if it does not exist. The file will* be created if it does not exist. An exception is thrown if the file* object exists but is a directory. An exception is thrown if the file* exists but cannot be written to. An exception is thrown if the parent* directory cannot be created.** @param file*            the file to open for output, must not be {@code null}* @param append*            if {@code true}, then bytes will be added to the*            end of the file rather than overwriting* @return a new {@link FileOutputStream} for the specified file* @throws IOException*             if the file object is a directory* @throws IOException*             if the file cannot be written to* @throws IOException*             if a parent directory needs creating but that fails*/public static FileOutputStream openOutputStream(File file, boolean append)throws IOException {if (file.exists()) {if (file.isDirectory()) {throw new IOException("File '" + file+ "' exists but is a directory");}if (file.canWrite() == false) {throw new IOException("File '" + file+ "' cannot be written to");}}else {File parent = file.getParentFile();if (parent != null) {if (!parent.mkdirs() && !parent.isDirectory()) {throw new IOException("Directory '" + parent+ "' could not be created");}}}return new FileOutputStream(file, append);}public static FileOutputStream openOutputStream(File file)throws IOException {return openOutputStream(file, false);}/*** Cleans a directory without deleting it.** @param directory*            directory to clean* @throws IOException*             in case cleaning is unsuccessful*/public static void cleanDirectory(File directory) throws IOException {if (!directory.exists()) {String message = directory + " does not exist";throw new IllegalArgumentException(message);}if (!directory.isDirectory()) {String message = directory + " is not a directory";throw new IllegalArgumentException(message);}File[] files = directory.listFiles();if (files == null) { // null if security restrictedthrow new IOException("Failed to list contents of " + directory);}IOException exception = null;for (File file : files) {try {forceDelete(file);}catch (IOException ioe) {exception = ioe;}}if (null != exception) {throw exception;}}// -----------------------------------------------------------------------/*** Deletes a directory recursively.** @param directory*            directory to delete* @throws IOException*             in case deletion is unsuccessful*/public static void deleteDirectory(File directory) throws IOException {if (!directory.exists()) {return;}cleanDirectory(directory);if (!directory.delete()) {String message = "Unable to delete directory " + directory + ".";throw new IOException(message);}}/*** Deletes a file. If file is a directory, delete it and all* sub-directories.* <p>* The difference between File.delete() and this method are:* <ul>* <li>A directory to be deleted does not have to be empty.</li>* <li>You get exceptions when a file or directory cannot be deleted.* (java.io.File methods returns a boolean)</li>* </ul>** @param file*            file or directory to delete, must not be {@code null}* @throws NullPointerException*             if the directory is {@code null}* @throws FileNotFoundException*             if the file was not found* @throws IOException*             in case deletion is unsuccessful*/public static void forceDelete(File file) throws IOException {if (file.isDirectory()) {deleteDirectory(file);}else {boolean filePresent = file.exists();if (!file.delete()) {if (!filePresent) {throw new FileNotFoundException("File does not exist: "+ file);}String message = "Unable to delete file: " + file;throw new IOException(message);}}}/*** Deletes a file, never throwing an exception. If file is a directory,* delete it and all sub-directories.* <p>* The difference between File.delete() and this method are:* <ul>* <li>A directory to be deleted does not have to be empty.</li>* <li>No exceptions are thrown when a file or directory cannot be deleted.</li>* </ul>** @param file*            file or directory to delete, can be {@code null}* @return {@code true} if the file or directory was deleted, otherwise*         {@code false}**/public static boolean deleteQuietly(File file) {if (file == null) {return false;}try {if (file.isDirectory()) {cleanDirectory(file);}}catch (Exception ignored) {}try {return file.delete();}catch (Exception ignored) {return false;}}/*** Makes a directory, including any necessary but nonexistent parent* directories. If a file already exists with specified name but it is* not a directory then an IOException is thrown.* If the directory cannot be created (or does not already exist)* then an IOException is thrown.** @param directory*            directory to create, must not be {@code null}* @throws NullPointerException*             if the directory is {@code null}* @throws IOException*             if the directory cannot be created or the file already exists*             but is not a directory*/public static void forceMkdir(File directory) throws IOException {if (directory.exists()) {if (!directory.isDirectory()) {String message = "File " + directory + " exists and is "+ "not a directory. Unable to create directory.";throw new IOException(message);}}else {if (!directory.mkdirs()) {// Double-check that some other thread or process hasn't made// the directory in the backgroundif (!directory.isDirectory()) {String message = "Unable to create directory " + directory;throw new IOException(message);}}}}/*** Returns the size of the specified file or directory. If the provided* {@link File} is a regular file, then the file's length is returned.* If the argument is a directory, then the size of the directory is* calculated recursively. If a directory or subdirectory is security* restricted, its size will not be included.** @param file*            the regular file or directory to return the size*            of (must not be {@code null}).** @return the length of the file, or recursive size of the directory,*         provided (in bytes).** @throws NullPointerException*             if the file is {@code null}* @throws IllegalArgumentException*             if the file does not exist.**/public static long sizeOf(File file) {if (!file.exists()) {String message = file + " does not exist";throw new IllegalArgumentException(message);}if (file.isDirectory()) {return sizeOfDirectory(file);}else {return file.length();}}/*** Counts the size of a directory recursively (sum of the length of all* files).** @param directory*            directory to inspect, must not be {@code null}* @return size of directory in bytes, 0 if directory is security*         restricted, a negative number when the real total*         is greater than {@link Long#MAX_VALUE}.* @throws NullPointerException*             if the directory is {@code null}*/public static long sizeOfDirectory(File directory) {checkDirectory(directory);final File[] files = directory.listFiles();if (files == null) { // null if security restrictedreturn 0L;}long size = 0;for (final File file : files) {size += sizeOf(file);if (size < 0) {break;}}return size;}/*** Checks that the given {@code File} exists and is a directory.** @param directory*            The {@code File} to check.* @throws IllegalArgumentException*             if the given {@code File} does not exist or is not a*             directory.*/private static void checkDirectory(File directory) {if (!directory.exists()) {throw new IllegalArgumentException(directory + " does not exist");}if (!directory.isDirectory()) {throw new IllegalArgumentException(directory+ " is not a directory");}}}