macOS Need help with indexing (Java or Obj-C)

1. Simple way:
Read a line. Does it contain the substring (e.g. "war")? If so, add to results (e.g. an NSMutableArray or a Java List). Repeat until EOF.

2. Faster but still simple-minded way:
Read a line. Add to collection of lines. Repeat until EOF.
To search, search the collection of lines (faster than reading a file every search).

3. Complex way:
Read a line. Break into words. Add words to set (NSSet or Java Set). Add set to collection of sets, e.g. an array or list where the index of the set is its number, e.g. 001.
To search, search the sets (faster than scanning a string every time, because a set can more quickly determine presence/absence). For anything less than 10,000 movies, I doubt the speed difference would be significant.

4. More complex way:
Read a line. Break into words. Add word to dictionary, with word as key and array of indexes as value. If word is already in dictionary, append index to array of values.
To search, use the word as key to dictionary. Value is array of indexes. Each index is the number of the movie whose title contains the word.


Notice how each approach is built from simpler pieces. So it's really just a question of Breaking It Down and figuring out what each individual piece is. If an individual piece is still too complex, then break it down, too.