Regex on InputStream

I have an open source project that can help with this, and it's much faster than a regex-based solution:

http://mtimmerm.github.io/dfalex/

In outline:

• use DfaBuilder to make a DFA that matches .*KEYWORD for each keyword. The easiest way to specify that pattern is Pattern.maybeRepeat(CharRange.ALL).then("KEYWORD");

• Call build() and you'll get a DfaState out. call state=state.getNextState(c) for each character of your input in turn, and whenever you're at the end of a keyword, state.getMatch() will tell you which keyword you've matched.

EDIT: The building is like this:

//The <Integer> here means you want integer results
DfaBuilder<Integer> builder = new DfaBuilder<>();

//Lets say you have a list of keywords:
for (int i=0; i<keywords.size(); ++i)
{
    Pattern pat = Pattern.maybeRepeat(CharRange.ALL)
        .then(keywords.get(i));
    builder.addPattern(pat, i);  //when this pattern matches, we get i out
}
DfaState<Integer> startState = builder.build(null);

And then use it like this:

DfaState<Integer> st = startState;
for (... each input character c ...)
{
    st = st.getNextState(c);
    //if this is non-null, then it's the index of the matched keyword
    //in the keywords list
    Integer match = st.getMatch();
}