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Editor to share with you what are the commonly used tool libraries in the Java world, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

Apache CommonsApache Commons has many sub-projects, and the common items are as follows:

BeanUtils

Provides a series of operations on java bean, reading and setting property values, and so on.

@ Data public class User {private String username; private String password;} User user = new User (); BeanUtils.setProperty (user, "username", "li"); BeanUtils.getProperty (user, "username")

Conversion between map and bean:

/ / bean- > map Map map = BeanUtils.describe (user); / / map- > bean BeanUtils.populate (user, map)

We usually use the hash in redis to put the object in the cache, as follows:

# set user information hset student name test hset student age 10

The utility class for converting map to bean is particularly useful in this scenario.

Codec

Common coding and decoding methods are encapsulated:

/ / Base64 Base64.encodeBase64String (byte [] binaryData) Base64.decodeBase64 (String base64String) / / MD5 DigestUtils.md5Hex (String data) / / URL URLCodec.decodeUrl (byte [] bytes); URLCodec.encodeUrl (BitSet urlsafe, byte [] bytes)

Collections

Operations such as intersection and difference:

/ / Null CollectionUtils.isEmpty (collA); / / intersection CollectionUtils.retainAll (collA, collB); / / Union CollectionUtils.union (collA, collB); / / difference CollectionUtils.subtract (collA, collB); / / Equal CollectionUtils.isEqualCollection (collA, collB)

I/O

Encapsulation of IO operation by IOUtils

/ / copy the stream IOUtils.copy (InputStream input, OutputStream output); / / read the content from the stream and change it to list List line = IOUtils.readLines (InputStream input, Charset encoding)

FileUtils

Encapsulation of file operation classes

File file = new File ("/ show/data.text"); / / read the file List lines = FileUtils.readLines (file, "UTF-8") by line; / / write the string to the file FileUtils.writeStringToFile (file, "test", "UTF-8"); / / copy the FileUtils.copyFile (srcFile, destFile)

Lang

StringUtils the following assertion test passed

/ / implementation of isEmpty cs = = null | | cs.length () = = 0; return true assertEquals (true, StringUtils.isEmpty (")); assertEquals (true, StringUtils.isBlank (null)); assertEquals (true, StringUtils.isBlank (")); / / blank assertEquals (true, StringUtils.isBlank (")); / / enter assertEquals (true, StringUtils.isBlank ("))

Pair and Triple when you want to return 2 or 3 values, but these values are not related, there is no need to encapsulate an object separately, you can use the following data structure to return Pair or Triple objects

Pair pair = new ImmutablePair (1Jue 2); / / 12 System.out.println (pair.getLeft () + "+" + pair.getRight ()); Triple triple = new ImmutableTriple (1PMI 2); / / 1 23 System.out.println (triple.getLeft () + "+ triple.getMiddle () +" + triple.getRight ())

Google Guava

Creation of a collection

/ / creation of ordinary sets Listlist = Lists.newArrayList (); Setset = Sets.newHashSet (); / / creation of immutable sets ImmutableListlist = ImmutableList.of ("a", "b", "c"); ImmutableSetset = ImmutableSet.of ("a", "b")

Immutable collections are thread-safe and cannot be changed halfway because methods such as add are declared expired and an exception is thrown.

/ / creation of ordinary sets List list = Lists.newArrayList (); Set set = Sets.newHashSet (); / / creation of immutable sets ImmutableList list = ImmutableList.of ("a", "b", "c"); ImmutableSet set = ImmutableSet.of ("a", "b")

Various cool techs collections

/ / use java Map map = new HashMap (); / / use guava Multimap map = ArrayListMultimap.create (); map.put ("key1", 1); map.put ("key1", 2); / / [1,2] System.out.println (map.get ("key1"))

2 keys map a value

Table table = HashBasedTable.create (); table.put ("a", "a", 1); table.put ("a", "b", 2); / / 2 System.out.println (table.get ("a", "b"))

There are many other various types of collections that will no longer be introduced.

Stop watch

View the run time of a piece of code

Stopwatch stopwatch = Stopwatch.createStarted (); / / do something long second = stopwatch.elapsed (TimeUnit.SECONDS)

TimeUnit can specify time precision

Joda Time

Before jdk1.8, only java.util.Date and java.util.Calendar were commonly used in date manipulation classes, but the ease of use of these two classes was so poor that SimpleDateFormat was not thread-safe. This forces users to choose third-party date manipulation classes, and Joda Time is one of the best.

The api of the two is very similar, if the company's jdk version is above 1.8, it is recommended to use jdk1.8 's new date class, and if it is below 1.8, it is recommended to use Joda Time.

These are all the contents of this article entitled "what are the common tool libraries in the Java world?" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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