常用的Java工具类
纵然，自己手写工具方法会很爽，但有些工具类还是值得参考：
Display-----
?
The bread and butter of the commons-lang library, this utility class includes some methods that should seriously have been included in String long time ago.
?
StringUtils.isEmpty(null) && StringUtils.isEmpty(""); // trueStringUtils.isBlank(" \n\t"); // trueStringUtils.substringAfterLast("foo.bar.baz", "."); // "baz"StringUtils.substringBeforeLast("foo.bar.baz", "."); // "foo.bar"StringUtils.split("foo.bar.baz", '.'); // { "foo", "bar", "baz" }StringUtils.split("foo, bar,baz", ", "); // { "foo", "bar", "baz" }StringUtils.leftPad("1", 3, '0'); // "001"??
A must-have for the rare occasions where you need to manipulate files by hand. Both are pretty much alike (FileUtils for File, IOUtils for InputStream and Reader classes) and come bundled in commons-io.
?
File file1;File file2;InputStream inputStream;OutputStream outputStream;// copy one file into anotherFileUtils.copyFile(file1, file2);IOUtils.copy(inputStream, outputStream);// read a file into a StringString s1 = FileUtils.readFileToString(file1);String s2 = IOUtils.toString(inputStream);// read a file into a list of Strings, one item per lineList<String> l1 = FileUtils.readLines(file1);List<String> l2 = IOUtils.readLines(inputStream);// put this in your finally() clause after manipulating streamsIOUtils.closeQuietly(inputStream);// return the list of xml and text files in the specified folder and any subfoldersCollection<File> c1 = FileUtils.listFiles(file1, { "xml", "txt" }, true);// copy one folder and its contents into anotherFileUtils.copyDirectoryToDirectory(file1, file2);// delete one folder and its contentsFileUtils.deleteDirectory(file1);?
ETC
?
This is the best implementation of a collections extension that I know of. Some of these are shouting to be included in the JDK:
?
// create an ArrayList with three argumentsList<String> list = Lists.newArrayList("foo", "bar", "baz");// notice that there is no generics or class cast,// and still this line does not generate a warning.Set<String> s = Sets.newConcurrentHashSet();// intersect and union are basic features of a Set, if you ask meSet<String> s = Sets.intersect(s1, s2);// Example of multiple values in a MapListMultimap<String, Validator> validators = new ArrayListMultimap<String, Validator>();validators.put("save", new RequiredValidator());validators.put("save", new StringValidator());validators.put("delete", new NumberValidator());validators.get("save"); // { RequiredValidator, StringValidator }validators.get("foo"); // empty List (not null)validators.values(); // { RequiredValidator, StringValidator, NumberValidator }??
原文：?My Top List of Java Tools
via ?http://java.dzone.com/articles/my-top-list-java-tools
reference :?利用org.apache.commons.io.FileUtils快速读写文件
?http://www.cnblogs.com/hellofei/archive/2010/04/10/1707131.html
?