Printing the number of times the word appears from a txt file

Question

I'm trying to find the number of times the word "the" appears in a txt file. With the code below, I keep getting the 0 as my output when it should be 4520. I'm using the delimiter to separate "the", but it doesn't seem to count it at all. The delimiter worked when I counted all words using "[^a-zA-Z]+".

in.useDelimiter("[^the]+");
while (in.hasNext()) {
    String words = in.next();
    words = words.toLowerCase();
    wordCount++;
}
System.out.println("The total number of 'the' is " + theWord);

Answer 1

Use \\b(?i)(the)\\b as the regex where \\b stands for the word boundary, i stands for case insensitive and (the) is for the as a whole. Note that [] checks for individual characters enclosed by it, not for the enclosed text as a whole.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = null;
        try {
            in = new Scanner(new File("file.txt"));
            int wordCount = 0, len;
            while (in.hasNextLine()) {
                len = in.nextLine().split("\\b(?i)(the)\\b").length;
                wordCount = len == 0 ? wordCount + 1 : wordCount + len - 1;
            }
            in.close();
            System.out.println("The total number of 'the' is " + wordCount);
        } catch (FileNotFoundException e) {
            System.out.println("File does not exist");
        }
    }
}

Output:

The total number of 'the' is 5

Content of file.txt:

The cat jumped over the rat.
The is written as THE in capital letter.
He gave them the sword.

Answer 2

In Java 9+, you can count the number of times a word occurs in a text file as follows:

static long countWord(String filename, String word) throws IOException {
    Pattern p = Pattern.compile("\\b" + Pattern.quote(word) + "\\b", Pattern.CASE_INSENSITIVE);
    return Files.lines(Paths.get(filename)).flatMap(s -> p.matcher(s).results()).count();
}

Test

System.out.println(countWord("test.txt", "the"));

test.txt

The quick brown fox
jumps over the lazy dog

Output

2

Java 8 version:

static int countWord(String filename, String word) throws IOException {
    Pattern p = Pattern.compile("\\b" + Pattern.quote(word) + "\\b", Pattern.CASE_INSENSITIVE);
    return Files.lines(Paths.get(filename)).mapToInt(s -> {
        int count = 0;
        for (Matcher m = p.matcher(s); m.find(); )
            count++;
        return count;
    }).sum();
}

Java 7 version:

static int countWord(String filename, String word) throws IOException {
    Pattern p = Pattern.compile("\\b" + Pattern.quote(word) + "\\b", Pattern.CASE_INSENSITIVE);
    int count = 0;
    try (BufferedReader in = Files.newBufferedReader(Paths.get(filename), StandardCharsets.UTF_8)) {
        for (String line; (line = in.readLine()) != null; )
            for (Matcher m = p.matcher(line); m.find(); )
                count++;
    }
    return count;
}

---

UPDATE

Full code for a Java 7+ version, without use of a method, and using the much slower Scanner, since OP seems to have trouble copy/pasting the methods above into their code.

import java.io.File;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {
    public static void main(String[] args) throws Exception {
        int count = 0;
        try (Scanner in = new Scanner(new File("test.txt"))) {
            Pattern p = Pattern.compile("\\bthe\\b", Pattern.CASE_INSENSITIVE);
            while (in.hasNextLine())
                for (Matcher m = p.matcher(in.nextLine()); m.find(); )
                    count++;
        }
        System.out.println("The total number of 'the' is " + count);
    }
}

For comparison, the full version using the first method in this answer would be:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.regex.Pattern;

public class Test {
    public static void main(String[] args) throws IOException {
        System.out.println("The total number of 'the' is " + countWord("test.txt", "the"));
    }
    static long countWord(String filename, String word) throws IOException {
        Pattern p = Pattern.compile("\\b" + Pattern.quote(word) + "\\b", Pattern.CASE_INSENSITIVE);
        return Files.lines(Paths.get(filename)).flatMap(s -> p.matcher(s).results()).count();
    }
}