code: @Override
  	public DestinationPatternsMessageCondition combine(
  			DestinationPatternsMessageCondition other) {
  		Set<String> result = new LinkedHashSet<>();
  		if (!this.patterns.isEmpty() && !other.patterns.isEmpty()) {
  			for (String pattern1 : this.patterns) {
  				for (String pattern2 : other.patterns) {
  					result.add(this.pathMatcher.combine(pattern1, pattern2));
  				}
  			}
  		}
  		else if (!this.patterns.isEmpty()) {
  			result.addAll(this.patterns);
  		}
  		else if (!other.patterns.isEmpty()) {
  			result.addAll(other.patterns);
  		}
  		else {
  			result.add("");
  		}
  		return new DestinationPatternsMessageCondition(result, this.pathMatcher);
  	}
docs: Returns a new instance with URL patterns from the current instance ("this") and the
  "other" instance as follows:
  <ul>
  <li>If there are patterns in both instances, combine the patterns in "this" with
  the patterns in "other" using
  {@link org.springframework.util.PathMatcher#combine(String, String)}.
  <li>If only one instance has patterns, use them.
  <li>If neither instance has patterns, use an empty String (i.e. "").
  </ul>