• TitleMatcher.java

  • § 
    package MusicLandscape.util.matcher;

import MusicLandscape.entities.Track;
import MusicLandscape.util.MyMatcher;

import java.util.regex.Pattern;
  • §

    The only interesting thing I did here is that in matches() I augment the string pattern with some regular expression features.

    /**
 * Encapsulates the concept of matching a track based on its title.
 * <p>
 * This class is used to test whether a given track's title starts with a certain string,
 * the starting string being the pattern of this matcher.
 * <p>
 * The pattern is a simple string. Null patterns are not accepted.
 *
 * @author Jonas Altrock (ew20b126@technikum-wien.at)
 * @version 1
 * @since ExerciseSheet05
 */
public class TitleMatcher extends MyMatcher<Track> {
    /**
     * The pattern to match the beginning of a Track title.
     */
    private String pattern;

    /**
     * Creates a Matcher object with a specified pattern.<br>
     *
     * @param pat the pattern of this matcher
     */
    public TitleMatcher(String pat) {
        super(pat);

        if (pat == null) {
            throw new NullPointerException("TitleMatcher does not accept null as pattern!");
        }
    }

    /**
     * Matches an object against the pattern of this matcher.
     *
     * @param track the object to match
     * @return whether t matches the pattern of this matcher.
     */
    @Override
    public boolean matches(Track track) {
  • §
    • the caret ^ means “at the start of the string”. This matcher will only match if the title of the track starts with the pattern.
    • .* means any character (.) repeated zero or more times (*). That is regular expression pattern for “eat the rest of the string”. This is not really necessary, but I try to always write my regular expressions so that they match the full input string.
            return track.getTitle().matches("^" + pattern + ".*");
    }

    /**
     * Sets the pattern of this matcher.
     * <p>
     * Null is not accepted.
     *
     * @param pat the pattern to set
     */
    @Override
    public void setPattern(String pat) {
        if (pat == null) {
            return;
        }

        pattern = pat;
    }

    /**
     * Gets the pattern of this matcher.
     * <p>
     * The pattern is returned in a format that is considered valid in setPattern.
     *
     * @return the pattern
     */
    @Override
    public String getPattern() {
        return pattern;
    }

    /**
     * the string representation is <kbd>title starts with (PATTERN)</kbd>
     *
     * @return a string representation of the object.
     */
    @Override
    public String toString() {
        return "title starts with (" + pattern + ")";
    }
}