由于Android项目忙完，苦于学习方向迷失，决定开一个进度，学习解析commons-IO包，提高JAVA水平，学习JAVA IO部分。
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废话不多说，进入正题。
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1.
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class="java" name="code">//-----------------------------------------------------------------------
/**
* Compares the contents of two files to determine if they are equal or not.
* <p>
* This method checks to see if the two files are different lengths
* or if they point to the same file, before resorting to byte-by-byte
* comparison of the contents.
* <p>
* Code origin: Avalon
*
* @param file1 the first file
* @param file2 the second file
* @return true if the content of the files are equal or they both don't
* exist, false otherwise
* @throws IOException in case of an I/O error
*/
public static boolean contentEquals(File file1, File file2) throws IOException {
boolean file1Exists = file1.exists();
if (file1Exists != file2.exists()) {
return false;
}
if (!file1Exists) {
// two not existing files are equal
return true;
}
if (file1.isDirectory() || file2.isDirectory()) {
// don't want to compare directory contents
throw new IOException("Can't compare directories, only files");
}
if (file1.length() != file2.length()) {
// lengths differ, cannot be equal
return false;
}
if (file1.getCanonicalFile().equals(file2.getCanonicalFile())) {
// same file
return true;
}
InputStream input1 = null;
InputStream input2 = null;
try {
input1 = new FileInputStream(file1);
input2 = new FileInputStream(file2);
return IOUtils.contentEquals(input1, input2);
} finally {
IOUtils.closeQuietly(input1);
IOUtils.closeQuietly(input2);
}
}
这个函数用来比较两个file里面的文件是否相同。
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比较策略：
1.判断是否有一个存在一个不存在（两个不存在也算相同）
2.判断两个是不是至少一个是目录（不能比较目录内容）
3.判断两个文件的长度是否相同，不同则返回false
4.应用File.getCanonicalFile()这个函数返回文件路径判断是不是指向同一个文件
5.最后才用inputstream导入两个文件，使用IOUtils.contentEquals(input1, input2)判断内容是否相等
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2.
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/**
* Compares the contents of two files to determine if they are equal or not.
* <p>
* This method checks to see if the two files point to the same file,
* before resorting to line-by-line comparison of the contents.
* <p>
*
* @param file1 the first file
* @param file2 the second file
* @param charsetName the character encoding to be used.
* May be null, in which case the platform default is used
* @return true if the content of the files are equal or neither exists,
* false otherwise
* @throws IOException in case of an I/O error
* @since 2.2
* @see IOUtils#contentEqualsIgnoreEOL(Reader, Reader)
*/
public static boolean contentEqualsIgnoreEOL(File file1, File file2, String charsetName) throws IOException {
boolean file1Exists = file1.exists();
if (file1Exists != file2.exists()) {
return false;
}
if (!file1Exists) {
// two not existing files are equal
return true;
}
if (file1.isDirectory() || file2.isDirectory()) {
// don't want to compare directory contents
throw new IOException("Can't compare directories, only files");
}
if (file1.getCanonicalFile().equals(file2.getCanonicalFile())) {
// same file
return true;
}
Reader input1 = null;
Reader input2 = null;
try {
if (charsetName == null) {
input1 = new InputStreamReader(new FileInputStream(file1));
input2 = new InputStreamReader(new FileInputStream(file2));
} else {
input1 = new InputStreamReader(new FileInputStream(file1), charsetName);
input2 = new InputStreamReader(new FileInputStream(file2), charsetName);
}
return IOUtils.contentEqualsIgnoreEOL(input1, input2);
} finally {
IOUtils.closeQuietly(input1);
IOUtils.closeQuietly(input2);
}
}
本函数和上一条基本相同，区别在于：
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Reader input1 = null;
Reader input2 = null;
try {
if (charsetName == null) {
input1 = new InputStreamReader(new FileInputStream(file1));
input2 = new InputStreamReader(new FileInputStream(file2));
} else {
input1 = new InputStreamReader(new FileInputStream(file1), charsetName);
input2 = new InputStreamReader(new FileInputStream(file2), charsetName);
}
return IOUtils.contentEqualsIgnoreEOL(input1, input2);
} finally {
IOUtils.closeQuietly(input1);
IOUtils.closeQuietly(input2);
}
这里使用了charsetName，用以获取编码后的字符流
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*学习：
InputStreamReader的创建（使用charsetName参数编码FileInputStream获取的字节）
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3.
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public static File toFile(URL url) {
if (url == null || !"file".equalsIgnoreCase(url.getProtocol())) {
return null;
} else {
String filename = url.getFile().replace('/', File.separatorChar);
filename = decodeUrl(filename);
return new File(filename);
}
}
一个用于把file协议的url转换为File类型的函数
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4.
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static String decodeUrl(String url) {
String decoded = url;
if (url != null && url.indexOf('%') >= 0) {
int n = url.length();
StringBuffer buffer = new StringBuffer();
ByteBuffer bytes = ByteBuffer.allocate(n);
for (int i = 0; i < n;) {
if (url.charAt(i) == '%') {
try {
do {
byte octet = (byte) Integer.parseInt(url.substring(i + 1, i + 3), 16);
bytes.put(octet);
i += 3;
} while (i < n && url.charAt(i) == '%');
continue;
} catch (RuntimeException e) {
// malformed percent-encoded octet, fall through and
// append characters literally
} finally {
if (bytes.position() > 0) {
bytes.flip();
buffer.append(UTF8.decode(bytes).toString());
bytes.clear();
}
}
}
buffer.append(url.charAt(i++));
}
decoded = buffer.toString();
}
return decoded;
}
转换URL出现问题时的优化处理
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（存疑）
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5.
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public static File[] toFiles(URL[] urls) {
if (urls == null || urls.length == 0) {
return EMPTY_FILE_ARRAY;
}
File[] files = new File[urls.length];
for (int i = 0; i < urls.length; i++) {
URL url = urls[i];
if (url != null) {
if (url.getProtocol().equals("file") == false) {
throw new IllegalArgumentException(
"URL could not be converted to a File: " + url);
}
files[i] = toFile(url);
}
}
return files;
}
Converts each of an array of URL to a File.
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刚才函数toFile()的数组版本
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6.
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public static URL[] toURLs(File[] files) throws IOException {
URL[] urls = new URL[files.length];
for (int i = 0; i < urls.length; i++) {
urls[i] = files[i].toURI().toURL();
}
return urls;
}
Converts each of an array of File to a URL.
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7.
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public static void copyFileToDirectory(File srcFile, File destDir) throws IOException {
copyFileToDirectory(srcFile, destDir, true);
}
Copies a file to a directory preserving the file date.
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8.
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public static void copyFileToDirectory(File srcFile, File destDir, boolean preserveFileDate) throws IOException {
if (destDir == null) {
throw new NullPointerException("Destination must not be null");
}
if (destDir.exists() && destDir.isDirectory() == false) {
throw new IllegalArgumentException("Destination '" + destDir + "' is not a directory");
}
File destFile = new File(destDir, srcFile.getName());
copyFile(srcFile, destFile, preserveFileDate);
}
刚才函数7的完整版本：
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1.确保目标地址不是空的
2.确保目标地址存在，并且不是文件
3.对源文件和目标文件的保护在copyFile里做了，所以这里只做对目标目录的保护。
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9.
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public static void copyFile(File srcFile, File destFile) throws IOException {
copyFile(srcFile, destFile, true);
}
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包装函数，重载默认保存date
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10.
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public static void copyFile(File srcFile, File destFile,
boolean preserveFileDate) throws IOException {
if (srcFile == null) {
throw new NullPointerException("Source must not be null");
}
if (destFile == null) {
throw new NullPointerException("Destination must not be null");
}
if (srcFile.exists() == false) {
throw new FileNotFoundException("Source '" + srcFile + "' does not exist");
}
if (srcFile.isDirectory()) {
throw new IOException("Source '" + srcFile + "' exists but is a directory");
}
if (srcFile.getCanonicalPath().equals(destFile.getCanonicalPath())) {
throw new IOException("Source '" + srcFile + "' and destination '" + destFile + "' are the same");
}
File parentFile = destFile.getParentFile();
if (parentFile != null) {
if (!parentFile.mkdirs() && !parentFile.isDirectory()) {
throw new IOException("Destination '" + parentFile + "' directory cannot be created");
}
}
if (destFile.exists() && destFile.canWrite() == false) {
throw new IOException("Destination '" + destFile + "' exists but is read-only");
}
doCopyFile(srcFile, destFile, preserveFileDate);
}
策略学习：
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目标文件和源文件的保护监测
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11.
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public static long copyFile(File input, OutputStream output) throws IOException {
final FileInputStream fis = new FileInputStream(input);
try {
return IOUtils.copyLarge(fis, output);
} finally {
fis.close();
}
}
从一个input文件中拷贝bytes进入output输出流，注意：
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IOUtils.copyLarge(fis, output)这个方法内部使用了buffer，所以不需要使用BufferedInputStream
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12.
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private static void doCopyFile(File srcFile, File destFile, boolean preserveFileDate) throws IOException {
if (destFile.exists() && destFile.isDirectory()) {
throw new IOException("Destination '" + destFile + "' exists but is a directory");
}
FileInputStream fis = null;
FileOutputStream fos = null;
FileChannel input = null;
FileChannel output = null;
try {
fis = new FileInputStream(srcFile);
fos = new FileOutputStream(destFile);
input = fis.getChannel();
output = fos.getChannel();
long size = input.size();
long pos = 0;
long count = 0;
while (pos < size) {
count = size - pos > FILE_COPY_BUFFER_SIZE ? FILE_COPY_BUFFER_SIZE : size - pos;
pos += output.transferFrom(input, pos, count);
}
} finally {
IOUtils.closeQuietly(output);
IOUtils.closeQuietly(fos);
IOUtils.closeQuietly(input);
IOUtils.closeQuietly(fis);
}
if (srcFile.length() != destFile.length()) {
throw new IOException("Failed to copy full contents from '" +
srcFile + "' to '" + destFile + "'");
}
if (preserveFileDate) {
destFile.setLastModified(srcFile.lastModified());
}
}
使用nio中的FileChannel进行复制（传输文件内容），调用IOUtils.closeQuietly()关闭filechannel和I/Ostream
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最后用文件的length长度监测是否传输成功
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16. publicstaticvoidcopyDirectory(File srcDir, File destDir, FileFilter filter,booleanpreserveFileDate)throwsIOException { if(srcDir ==null) { thrownewNullPointerException("Source must not be null"); } if(destDir ==null) { thrownewNullPointerException("Destination must not be null"); } if(srcDir.exists() ==false) { thrownewFileNotFoundException("Source '"+ srcDir +"' does not exist"); } if(srcDir.isDirectory() ==false) { thrownewIOException("Source '"+ srcDir +"' exists but is not a directory"); } if(srcDir.getCanonicalPath().equals(destDir.getCanonicalPath())) { thrownewIOException("Source '"+ srcDir +"' and destination '"+ destDir +"' are the same"); } ? // Cater for destination being directory within the source directory (see IO-141) List<String> exclusionList =null; if(destDir.getCanonicalPath().startsWith(srcDir.getCanonicalPath())) { File[] srcFiles = filter ==null? srcDir.listFiles() : srcDir.listFiles(filter); if(srcFiles !=null&& srcFiles.length> 0) { exclusionList =newArrayList<String>(srcFiles.length); for(File srcFile : srcFiles) { File copiedFile =newFile(destDir, srcFile.getName()); exclusionList.add(copiedFile.getCanonicalPath()); } } } doCopyDirectory(srcDir, destDir, filter, preserveFileDate, exclusionList); } ? ? ? 这个函数加入了一个filter对复制操作的file加以过滤 ? 注意：这里有一个假如destDir是srcDir的子目录的附加操作 // Cater for destination being directory within the source directory (see IO-141) List<String> exclusionList =null; if(destDir.getCanonicalPath().startsWith(srcDir.getCanonicalPath())) { File[] srcFiles = filter ==null? srcDir.listFiles() : srcDir.listFiles(filter); if(srcFiles !=null&& srcFiles.length> 0) { exclusionList =newArrayList<String>(srcFiles.length); for(File srcFile : srcFiles) { File copiedFile =newFile(destDir, srcFile.getName()); exclusionList.add(copiedFile.getCanonicalPath()); } } } ? exclusionList是要排除的文件路径String列表（因为本来就在desDir里面），要作为参数传入下一个docopy()方法中 ? ? 17. privatestaticvoiddoCopyDirectory(FilesrcDir, File destDir, FileFilter filter, booleanpreserveFileDate, List<String> exclusionList)throwsIOException { // recurse File[] srcFiles = filter ==null?srcDir.listFiles() :srcDir.listFiles(filter); if(srcFiles ==null) {// null if abstract pathname does not denote a directory, or if an I/O error occurs thrownewIOException("Failed to list contents of "+srcDir); } if(destDir.exists()) { if(destDir.isDirectory() ==false) { thrownewIOException("Destination '"+ destDir +"' exists but is not a directory"); } }else{ if(!destDir.mkdirs() && !destDir.isDirectory()) { thrownewIOException("Destination '"+ destDir +"' directory cannot be created"); } } if(destDir.canWrite() ==false) { thrownewIOException("Destination '"+ destDir +"' cannot be written to"); } for(File srcFile : srcFiles) { File dstFile =newFile(destDir, srcFile.getName()); if(exclusionList ==null|| !exclusionList.contains(srcFile.getCanonicalPath())) { if(srcFile.isDirectory()) { doCopyDirectory(srcFile, dstFile, filter, preserveFileDate, exclusionList); }else{ doCopyFile(srcFile, dstFile, preserveFileDate); } } } ? // Do this last, as the above has probably affected directory metadata if(preserveFileDate) { destDir.setLastModified(srcDir.lastModified()); } } ? ? 注意： 1.递归调用，反复打开子目录复制文件 2.排除列表的操作 ? ? 20. publicstaticvoidcopyInputStreamToFile(InputStream source, File destination)throwsIOException { try{ FileOutputStream output =openOutputStream(destination); try{ IOUtils.copy(source, output); output.close();// don't swallow close Exception if copy completes normally }finally{ IOUtils.closeQuietly(output); } }finally{ IOUtils.closeQuietly(source); } } ? 使用IOUtils.copy()函数复制source流到output流（目标文件输出流） ? ? 21. publicstaticvoiddeleteDirectory(File directory)throwsIOException { if(!directory.exists()) { return; } ? if(!isSymlink(directory)) { cleanDirectory(directory); } ? if(!directory.delete()) { String message = "Unable to delete directory "+ directory +"."; thrownewIOException(message); } } ? ? isSymlink(directory)貌似和windows没关系？？暂时存疑 调用cleanDirectory清空目录，然后删除目录本身 ? ? 22. publicstaticbooleandeleteQuietly(File file) { if(file ==null) { returnfalse; } try{ if(file.isDirectory()) { cleanDirectory(file); } }catch(Exception ignored) { } ? try{ returnfile.delete(); }catch(Exception ignored) { returnfalse; } } ? 本身Doc的描述：Deletes a file, never throwing an exception. If file is a directory, delete it and all sub-directories.
The difference between File.delete() and this method are:
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