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.

Why don't you just strip all punctuation from the string with replaceAll and then split it around blank character groups (using the regex \\s+).  Making it all one case will probably help too.

String str = "This test string is a test.";
str = str.toLowerCase();
str = str.replaceAll(".", " "); // simple example; the first parameter uses regex/real expression codes
String[] ary = str.split("\\s+");

Array ary should have the contents: [this][test][string][is][a][test]