code: public synchronized DirectoryScanner addExcludes(String[] excludes) {
          if (excludes != null && excludes.length > 0) {
              if (this.excludes != null && this.excludes.length > 0) {
                  String[] tmp = new String[excludes.length
                                            + this.excludes.length];
                  System.arraycopy(this.excludes, 0, tmp, 0,
                                   this.excludes.length);
                  for (int i = 0; i < excludes.length; i++) {
                      tmp[this.excludes.length + i] =
                          normalizePattern(excludes[i]);
                  }
                  this.excludes = tmp;
              } else {
                  setExcludes(excludes);
              }
          }
          return this;
      }
docs: Add to the list of exclude patterns to use. All '/' and '\'
  characters are replaced by <code>File.separatorChar</code>, so
  the separator used need not match <code>File.separatorChar</code>.
  <p>
  When a pattern ends with a '/' or '\', "**" is appended.
  
  @param excludes A list of exclude patterns.
  May be <code>null</code>, in which case the
  exclude patterns don't get changed at all.
  
  @since Ant 1.6.3