First words

A string contains many words. These are separated by spaces. To create a caption of the text, we sometimes need to get the first words from the string.

With a loop, and a char-testing algorithm, we can extract the first N words from a string. We use substring() to extract the first part from the text.

An example

Here is the firstWords method. This method receives two arguments: the string we want to get the first words from, and the number of words to extract. It uses a for-loop.

public class Program {

    public static String firstWords(String input, int words) {
        for (int i = 0; i < input.length(); i++) {
            // When a space is encountered, reduce words remaining by 1.
            if (input.charAt(i) == ' ') {
            words--;
        }
        // If no more words remaining, return a substring.
        if (words == 0) {
            return input.substring(0, i);
        }
    }
    // Error case.
    return "";
}

public static void main(String[] args) {

    String value = "One two three four five.";
    System.out.println(value);

    // Test firstWords on the first 3 and 4 words.
    String words3 = firstWords(value, 3);
    System.out.println(words3);
    String words4 = firstWords(value, 4);
    System.out.println(words4);
}
}
One two three four five.
One two three
One two three four

Some issues

The method does not handle an invalid number of words. If you specify a million words and there are not that many words, an empty string will be returned.

A learning exercise

When learning a programming language, writing many simple methods like this one is helpful. Many things can be accomplished with a simple char-testing loop.

This method extracts the first words from a string. This can be used to create brief summaries of text (or captions for images). First words are often sufficient for labels.