According to the project site on GitHub, The Guava project contains several of Google’s core libraries that we rely on in our Java-based projects: collections, caching, primitives support, concurrency libraries, common annotations, string processing, I/O, and so forth.

I’ll show you some cool features that could make you like Guava Libraries even more:

  • Multimaps
  • I’m pretty sure that at least one time in you life you have needed a Map<Foo, Collection<Bar>> or something similar, huh? If not, someday you will need it, and when you need, you will see the crap that is doing a lot of checks for a existing collection with some key and creating and adding it if it isn’t there.
  • Ordering - Basically, a fluent comparator class, with a lot of utilities… you will be surprised when you see how cow it is, and will ask yourself how could I live without it until now?, you can bet.
  • Objects#equal - A null safe equals method. Never write if(foo != null && bar != null && foo.equals(bar)) in your life again. BTW, take a look in all Object common methods , you can use Objects#firstNonNull(Object, Object), as example, while Elvis operator and Java 8 are not ready :)
  • @Nullable and other utilities to help you follow the Null Object Pattern.
  • IO Handling, the Files class e.g.. Want to read the lines of a text file? Are you opening a BufferedReader? Don’t do that:
Collection<String> lines = Files.readLines(mytxtFile, Charsets.UTF8);

Simple, uh?

  • Splitters and Joinners. Suppose that our text filed used in the other example contains a lot of columns divided by a pipe (|), now, how can we parse it? Simple! Iterate the collection of string provided by Files.readLines, and do something like:
Iterable<String> columns = Splitter
  .on('|')
  .trimResults()
  .omitEmptyStrings()
  .split(line);

Pretty easy :)

  • Preconditions plus a static import made your arguments, state and null check easy and clean, throwing the respective exceptions (IllegalStateException, IllegalArgumentException, NullPointerException, etc…).
  • Immutable collections types (Immutable Maps, Lists, Sets, etc…).
  • CharMatcher. pretty easy way to match characteres sequences, eg:
String phoneNumber = CharMatcher
  .DIGIT
  .retainFrom("my phone number is 123456789");
CharMatcher
  .inRange('a','z')
  .or(inRange('A','Z'));

  • There are also Functional classes, maybe you will want to use them.

  • EventBus. Basically, a better EventListener.

  • Caching. Make your app faster.

These are, IMHO, the best features in Guava. But, there is much more.

If you want to use it in a maven project, just add to your pom.xml:

<dependency>
	<groupId>com.google.guava</groupId>
	<artifactId>guava</artifactId>
	<version>15.0</version>
</dependency>

If you are not using maven, you can download the last version in this page.

The project still active, the last release (19) is from Dec 2015.

That’s all. Cheers.