If you need to run a brute­force attack against some Java classes, you may use John the Rip­per. Per­haps not the fastest vari­ant but very easy to set up:

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john –incre­men­tal –std­out | java –cp some.jar:. Digest

and Digest.java looks like this:

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Buffere­dReader stdin =  new Buffere­dReader (new Input­Stream­Reader(Sys­tem.in));

String user­In­put=””;
int i=0;
while ((user­In­put = stdin.read­Line()) != null) {
    if (i%500000==0) Sys­tem.out.print(”.”);
    i++;
    //do what­ever you need to do…
}

Quite easy, eh?