src/main/java/com/github/fge/grappa/matchers/join/JoinMatcherBootstrap.java
public JoinMatcherBuilder<V> using(@Nonnull final Object joining)
    {
        return new JoinMatcherBuilder<>(joined, parser, parser.toRule(joining));
    }
public JoinMatcherBuilder<V> using(@Nonnull final Object joining)
    {
        return new JoinMatcherBuilder<>(joined, parser, parser.toRule(joining));
    }
public JoinMatcherBuilder < V > using ( @ Nonnull final Object joining ) { return new JoinMatcherBuilder <> ( joined , parser , parser . toRule ( joining ) ) ; }
Define the joining rule

@param joining the rule
@return a new {@link JoinMatcherBuilder}

@see BaseParser#toRule(Object)
Define the joining rule