code: public void setOpaque( String scheme, String schemeSpecificPart )
      {
          if ( scheme == null || scheme.length() == 0
                  || schemeSpecificPart == null
                  || schemeSpecificPart.length() == 0
                  || schemeSpecificPart.indexOf( '/' ) > 0 )
          {
              throw new IllegalArgumentException( "Not a proper opaque URI." );
          }
  
          _opaque = true;
          setScheme( scheme );
          setSchemeSpecificPart( schemeSpecificPart );
          setUserInfo( null );
          setHost( null );
          setPort( UNDEFINED_PORT );
          setPath( null );
          setQuery( null );
      }
docs: Sets the URI to be opaque using the given scheme and
  schemeSpecificPart.
  <p> From {@link URI}: &quot;A URI is opaque if, and only
  if, it is absolute and its scheme-specific part does not begin with
  a slash character ('/'). An opaque URI has a scheme, a
  scheme-specific part, and possibly a fragment; all other components
  are undefined.&quot; </p>
  
  @param scheme the scheme component of this URI
  @param schemeSpecificPart the scheme-specific part of this URI