In short, Guava API Search lets you to type a query in the address bar, and provides you an autocomplete function.
In other words, with the Guava API Search extension you can search through the classes and interfaces included in the Guava Libraries (Google`s opensource core Java libraries.
To use Guava API Search type the keyword guava followed by a space, and by your search query in the omnibar. The Guava API Search extension will list any clases or interfaces whose simple names or fully-qualified names match the search query.
Selecting an autocompeted result and pressing enter will take you directly to the JavaDoc page for the given class or interface.