工具类收藏

Ignacio Coloma说道：作为一个软件开发者，缺乏想象力是最严重的罪过之一。我们经常把事情重复做一遍又一遍，但是我们很少改变这种方式，至少我是这样。经过这些年开发，在我的工具箱里面有了一些每个项目我都需要用到的工具，烦人的重复工作不再是我的事。

下面这些工具也许你已经用到，让我来仔细介绍它们：

StringUtils

这是象面包和奶油一样必须的通用语言库，这个实用工具类包括一些很早以前在String中未包含的重要方法。


Java代码
1.StringUtils.isEmpty(null) && StringUtils.isEmpty(""); // true    
2.StringUtils.isBlank("   \n\t");                       // true    
3.StringUtils.substringAfterLast("foo.bar.baz", ".");   // "baz"    
4.StringUtils.substringBeforeLast("foo.bar.baz", ".");  // "foo.bar"    
5.StringUtils.split("foo.bar.baz", '.');                // { "foo", "bar", "baz" }    
6.StringUtils.split("foo,  bar,baz", ", ");             // { "foo", "bar", "baz" }    
7.StringUtils.leftPad("1", 3, '0');                     // "001"   
StringUtils.isEmpty(null) && StringUtils.isEmpty(""); // true 
StringUtils.isBlank("   \n\t");                       // true 
StringUtils.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" 


IOUtils and FileUtils

在一种当你需要手动操作多个文件罕见情况下必须具备的工具，这两个工具很相似(FileUtils操作文件，IOUtils操作InputStream和Reader classes)，和捆绑常用IO.


Java代码
1.File file1;  
2.File file2;  
3.InputStream inputStream;  
4.OutputStream outputStream;  
5. 
6.// copy one file into another  
7.FileUtils.copyFile(file1, file2);  
8.IOUtils.copy(inputStream, outputStream);  
9. 
10.// read a file into a String  
11.String s1 = FileUtils.readFileToString(file1);  
12.String s2 = IOUtils.toString(inputStream);  
13. 
14.// read a file into a list of Strings, one item per line  
15.List<String> l1 = FileUtils.readLines(file1);  
16.List<String> l2 = IOUtils.readLines(inputStream);  
17. 
18.// put this in your finally() clause after manipulating streams  
19.IOUtils.closeQuietly(inputStream);  
20. 
21.// return the list of xml and text files in the specified folder and any subfolders  
22.Collection<File> c1 = FileUtils.listFiles(file1, { "xml", "txt" }, true);  
23. 
24.// copy one folder and its contents into another  
25.FileUtils.copyDirectoryToDirectory(file1, file2);  
26. 
27.// delete one folder and its contents  
28.FileUtils.deleteDirectory(file1); 
File file1;
File file2;
InputStream inputStream;
OutputStream outputStream;

// copy one file into another
FileUtils.copyFile(file1, file2);
IOUtils.copy(inputStream, outputStream);

// read a file into a String
String s1 = FileUtils.readFileToString(file1);
String s2 = IOUtils.toString(inputStream);

// read a file into a list of Strings, one item per line
List<String> l1 = FileUtils.readLines(file1);
List<String> l2 = IOUtils.readLines(inputStream);

// put this in your finally() clause after manipulating streams
IOUtils.closeQuietly(inputStream);

// return the list of xml and text files in the specified folder and any subfolders
Collection<File> c1 = FileUtils.listFiles(file1, { "xml", "txt" }, true);

// copy one folder and its contents into another
FileUtils.copyDirectoryToDirectory(file1, file2);

// delete one folder and its contents
FileUtils.deleteDirectory(file1);


Google collections

这是我所知道的最好的扩展实现包，其中一些被社区叫嚣着要加入JDK：


Java代码
1.// create an ArrayList with three arguments  
2.List<String> list = Lists.newArrayList("foo", "bar", "baz");  
3. 
4.// notice that there is no generics or class cast,  
5.// and still this line does not generate a warning.  
6.Set<String> s = Sets.newConcurrentHashSet();  
7. 
8.// intersect and union are basic features of a Set, if you ask me  
9.Set<String> s = Sets.intersect(s1, s2);  
10. 
11.// Example  of multiple values in a Map  
12.ListMultimap<String, Validator> validators = new ArrayListMultimap<String, Validator>();  
13.validators.put("save", new RequiredValidator());  
14.validators.put("save", new StringValidator());  
15.validators.put("delete", new NumberValidator());  
16. 
17.validators.get("save"); // { RequiredValidator, StringValidator }  
18.validators.get("foo");  // empty List (not null)  
19.validators.values();    // { RequiredValidator, StringValidator, NumberValidator } 
// create an ArrayList with three arguments
List<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 me
Set<String> s = Sets.intersect(s1, s2);

// Example  of multiple values in a Map
ListMultimap<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 }


java.util.concurrent

不是每个人都需要这么重的java.util.concurrent，但是很好用:


Java代码
1.// a map that may be modified (by the same or different thread) while being iterated  
2.Map<String, Something> repository = new ConcurrentHashMap<String, Something>();  
3. 
4.// same with lists. This one is only available with Java 6  
5.List<Something> list = new CopyOnWriteArrayList<Something>(); 
// a map that may be modified (by the same or different thread) while being iterated
Map<String, Something> repository = new ConcurrentHashMap<String, Something>();

// same with lists. This one is only available with Java 6
List<Something> list = new CopyOnWriteArrayList<Something>();


你有好的工具推荐吗？欢迎留言。
来自: java.dzone.com