Class StringsCompare

src/main/java/org/sfj/StringsCompare.java:41–426

Compare two string sequences (files, resource streams, anything that can be expressed as sequence of lines). Possibly ignore line endings, possible ignore leading and/or trailing whitespace, possibly ignore case. Useful for testing when you have an expected file as a resource, say, and need to co

 * need to compare it to output of some execution.
 */
public class StringsCompare {
  /**
   * A source of lines. Essentially, an iterator with IOExceptions. Also
   * supports the use of predicates to skip lines testing true.
   */
  interface LineSource extends Closeable {
    /**
     * Has a line?
     * @return ture if another line exists.
     * @throws IOException on error
     */
    boolean hasLine() throws IOException;

    /**
     * Fetch next line.
     * @return next line
     * @throws IOException on error
     */
    String nextLine() throws IOException;

    @Override
    default void close() throws IOException {

    }
  }

  /**
   * Predicate to skip no lines.
   */
  public static Predicate<String> SKIP_NONE = (s) -> false;

  /**
   * Predicate to skip whitespace only lines.
   */
  public static Predicate<String> SKIP_BLANK = (s) -> s.trim().length() == 0;

  /**
   * Predicate to skip empty lines.
   */
  public static Predicate<String> SKIP_EMPTY = (s) -> s.length() == 0;

  /**
   * Ident transform, use when you want no mapping done on strings.
   */
  public static final Function<String, String> IDENT = (s) -> s;

  /**
   * Mapping transform to remove leading whitespace.
   */
  public static final Function<String, String> TRIM_LEADING_WHITESPACE = (s) -> {
    int i = 0;
    for (; i < s.length(); i++) {
      if (!Character.isWhitespace(s.charAt(i))) {
        break;
      }
    }
    if (i > 0) {
      return s.substring(i);