String operations in Java

I'm learning about operations on strings, and I'm having trouble dealing with punctuation. Basically, I need to provide the count of each word in a given string. I have no problem with this, except that punctuation at the end of a word cannot be included.

For example, the string
"This test string is a test."
should yield to
this - 1
test - 2
string - 1
is - 1
a - 1

but instead I'm getting

test - 1
test. - 1

to further complicate matters, things like "..." is a word, and should be counted once. "derp.derp" is also a single word.

I have the logic, but I don't know how to execute it
if (word ends in punctuation and is preceded by non-punctuation)
   word = substring(0,word.length)

this gets pretty messy and I'm getting a lot of null pointers with spaces in between words for some reason.

I'll post some of my code after this.

You know what'd be useful? Regular expressions.