Find phrases from a text file in Java

Question

The goal is I am reading in a text file and finding certain words to replace. It will then replace the words and output a new text file that has the words replaced. My code works good for single words, but if I try to replace a phrase with a space, it doesn't work. What I have is a HashMap that contains what I need to search for in the file.

 HashMap<String, Integer> hm = new HashMap<>();

            hm.put("null",0);
            hm.put("max",1);
            hm.put("Do not repeat",2);
            hm.put("names",3);

I then iterate through the HashMap and replace the strings with the word if the file contains it.

                    for (String key : hm.keySet()) {
                        String check = key;
                        System.out.println(check);

                        text = text.toLowerCase(Locale.ROOT).replaceAll(check, "WRONG");
                    }
                    String new = text;

This isn't working if I have a space in the words like for "Do not repeat". How can I get this to work for phrases and not just single words? It completely skips over the phrases and outputs the new file with only the single words replaced.

BTW, if you're wanting to replace the literal string, you should consider quoting it, e.g. `Pattern.quote(check)`, to avoid surprising things with metacharacters. Or just use `replace`, ofc. — Andy Turner, Jan 25 '21 at 19:50
Thank you! I feel so silly! Do you happen to know a way to do this without turning the text file to lowercase? — Mark, Jan 25 '21 at 19:52
Yeah, I would like to check without having to change all the letters in the file to lowercase! — Mark, Jan 25 '21 at 19:53

Andy Turner · Accepted Answer · 2021-01-25T20:18:04.013

It's not to do with the spaces, it's because of the upper-cased D.

text.toLowerCase(Locale.ROOT)

will make a string containing only lower-cased letters, so "Do not repeat" will not be found in it.

You can make replaceAll case insensitive by passing the appropriate flag:

text = text.replaceAll("(?i)" + check, "WRONG");

Note that you might run into problems with metacharacters in the strings you are searching for. If you might include things with e.g. periods (.), you should quote check:

text = text.replaceAll("(?i)" + Pattern.quote(check), "WRONG");

Also, because you're not considering word boundaries, you might run into the Scunthorpe problem.

Perfect! Exactly what I wanted to learn!. Thank you! – Mark Jan 25 '21 at 19:57 — Mark, Jan 25 '21 at 19:57

Find phrases from a text file in Java

1 Answers1