Poly-SO 混合代码与 Apache Commons FileUtils 的比较：iterateFiles 和 listFiles
Apache commons-io 在 FileUtils 中有类似的方法 iterateFiles 和 listFiles，由 Bozho 建议。
参数检查以多种方式完成，但绝不是“System.exit(9)”！
他们比较为空，用文件类型检查它的存在（可用的方法），
他们在 listFiles-implementation 中使用静态的linkedList——poly 在书中建议。
他们重用该字段来匹配所有目录：
TrueFileFilter.INSTANCE
真实过滤器的单例实例（来自 Apache API，单例？）
这两个方法是唯一使用 IOFileFilter 作为参数的方法。
我不确定它的含义。他们肯定可以重用他们的代码。
有一些非常简洁——我认为不错——评估点，没有模糊的虚拟变量。
请看 (a?b:c) 的评估，省去愚蠢的傻瓜和 if 子句。
return listFiles(directory, filter,
(recursive ? TrueFileFilter.INSTANCE : FalseFileFilter.INSTANCE));
方法所在的 FileUtils 类只有 4 个字段值——每个字段大约有 2.5 个方法！
现在我为我的班级感到羞耻。
一个显着的区别是异常的使用。
他们使用它们，但是——显然是由于 FileUtils 类的不同目标——他们让用户来处理它们，列表中没有集中的集合。
没有额外的声明。
总结
- 相似之处：linkedList 和列表
- 区别：inits 更少，decs 更少，方法的字段密度更小——简洁
- 不同的目标：SO 的类最终用户案例，FileUtils 更多的后端
- 差异（自然）：在 SO 中处理异常，但在 FileUtils 中没有（也许这就是它如此干净的原因）
我喜欢 cmets，尤其是 source——我觉得，比起阅读琐碎的 API，更适合用于教育目的。希望你也:)
Apache Commons：FileUtils.java、listFiles、iterateFiles - 代码片段
/**
* Finds files within a given directory (and optionally its
* subdirectories). All files found are filtered by an IOFileFilter.
* <p>
* If your search should recurse into subdirectories you can pass in
* an IOFileFilter for directories. You don't need to bind a
* DirectoryFileFilter (via logical AND) to this filter. This method does
* that for you.
* <p>
* An example: If you want to search through all directories called
* "temp" you pass in <code>FileFilterUtils.NameFileFilter("temp")</code>
* <p>
* Another common usage of this method is find files in a directory
* tree but ignoring the directories generated CVS. You can simply pass
* in <code>FileFilterUtils.makeCVSAware(null)</code>.
*
* @param directory the directory to search in
* @param fileFilter filter to apply when finding files.
* @param dirFilter optional filter to apply when finding subdirectories.
* If this parameter is <code>null</code>, subdirectories will not be included in the
* search. Use TrueFileFilter.INSTANCE to match all directories.
* @return an collection of java.io.File with the matching files
* @see org.apache.commons.io.filefilter.FileFilterUtils
* @see org.apache.commons.io.filefilter.NameFileFilter
*/
public static Collection listFiles(
File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) {
if (!directory.isDirectory()) {
throw new IllegalArgumentException(
"Parameter 'directory' is not a directory");
}
if (fileFilter == null) {
throw new NullPointerException("Parameter 'fileFilter' is null");
}
//Setup effective file filter
IOFileFilter effFileFilter = FileFilterUtils.andFileFilter(fileFilter,
FileFilterUtils.notFileFilter(DirectoryFileFilter.INSTANCE));
//Setup effective directory filter
IOFileFilter effDirFilter;
if (dirFilter == null) {
effDirFilter = FalseFileFilter.INSTANCE;
} else {
effDirFilter = FileFilterUtils.andFileFilter(dirFilter,
DirectoryFileFilter.INSTANCE);
}
//Find files
Collection files = new java.util.LinkedList();
innerListFiles(files, directory,
FileFilterUtils.orFileFilter(effFileFilter, effDirFilter));
return files;
}
/**
* Allows iteration over the files in given directory (and optionally
* its subdirectories).
* <p>
* All files found are filtered by an IOFileFilter. This method is
* based on {@link #listFiles(File, IOFileFilter, IOFileFilter)}.
*
* @param directory the directory to search in
* @param fileFilter filter to apply when finding files.
* @param dirFilter optional filter to apply when finding subdirectories.
* If this parameter is <code>null</code>, subdirectories will not be included in the
* search. Use TrueFileFilter.INSTANCE to match all directories.
* @return an iterator of java.io.File for the matching files
* @see org.apache.commons.io.filefilter.FileFilterUtils
* @see org.apache.commons.io.filefilter.NameFileFilter
* @since Commons IO 1.2
*/
public static Iterator iterateFiles(
File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) {
return listFiles(directory, fileFilter, dirFilter).iterator();
}
//****剪掉一部分******//
/**
* Finds files within a given directory (and optionally its subdirectories)
* which match an array of extensions.
*
* @param directory the directory to search in
* @param extensions an array of extensions, ex. {"java","xml"}. If this
* parameter is <code>null</code>, all files are returned.
* @param recursive if true all subdirectories are searched as well
* @return an collection of java.io.File with the matching files
*/
public static Collection listFiles(
File directory, String[] extensions, boolean recursive) {
IOFileFilter filter;
if (extensions == null) {
filter = TrueFileFilter.INSTANCE;
} else {
String[] suffixes = toSuffixes(extensions);
filter = new SuffixFileFilter(suffixes);
}
return listFiles(directory, filter,
(recursive ? TrueFileFilter.INSTANCE : FalseFileFilter.INSTANCE));
}
/**
* Allows iteration over the files in a given directory (and optionally
* its subdirectories) which match an array of extensions. This method
* is based on {@link #listFiles(File, String[], boolean)}.
*
* @param directory the directory to search in
* @param extensions an array of extensions, ex. {"java","xml"}. If this
* parameter is <code>null</code>, all files are returned.
* @param recursive if true all subdirectories are searched as well
* @return an iterator of java.io.File with the matching files
* @since Commons IO 1.2
*/
public static Iterator iterateFiles(
File directory, String[] extensions, boolean recursive) {
return listFiles(directory, extensions, recursive).iterator();
}