java - How to use classes in Referenced Libraries in Eclipse

Question

I have imported the algs4.jar file as a referenced library as seen above. All seems to be fine but I can't seem to use or access any of the classes in the library.

Is there an import statement I'm missing?

Image reference:

Note how I'm trying to use BinarySearch from the referenced library but it is not offering me an option to use or import it.

Answer 1

I am not sure, I did not try this. Some interpretations though.

Is this a standard library or someone created it by himself and gave you?

The problem is class BinarySearch is in default package. You will not be able to import it. If this library is created by you, or by any of your friend, you need to ask your friend to move all classes from default package to a good namespace and then re-create the jar.

If class is accessible, ctr + shift + o should import the class.