For example, say I have a string and it has the letters:RDNALThis is not an actual English word or it doesn't start an actual english word, so the program would skip this string and would avoid it.But say the string was:MICROThis is the first 5 letters of an actual word, like microwave or microprocessor, etc. And it actually is a wordI want to write a program in Java that will be able to see if a given string contains any block of strings that belong to a potential word.I'm playing a game where I have to decypher a secret language, so I set numbers equal to each character, and now I want to run each number and put an English letter to each number and see if it possibly spells out a word. Is this possible or is this just way too massive to do? I'm asking here because I'm not sure if it's impossible or possible based on the number of combinations or some kind of program to reference to check words against. I think I can write the program to add a letter to each number then rotate through and spit out a string, but I am not sure about comparing the string to an English word. 
Program to look at the first say 5 characters of a word and return a string if that string is actually the first 5 characters of a word?
java;design patterns;algorithms;open source;security
Possible? Yes. You should be able to download a word list (example) and compare each word's first five letters with your string, however it isn't going to be very efficient. IMHO.If you need to check more than a few words, then it may be useful to look into optimizations. For example, you could precompute a giant HashMap which contains all valid 5 letter combinations and easily check against that.