Assume a given query which uses pragma output:format '_JAVA_' with CONSTRUCT:

SPARQL DEFINE output:format '_JAVA_'
   CONSTRUCT { ?s ?p ?o }
WHERE
  {
    ?s ?p ?o .
    FILTER (?s = iri(?::0))
  }
LIMIT 1

In order to work correctly, the query should be modified to:

SPARQL DEFINE output:format '_JAVA_'
   CONSTRUCT { `iri(?::0)` ?p ?o }
WHERE
  {
    `iri(?::0)` ?p ?o
  }
LIMIT 1

Equivalent variant of the query is also:

SPARQL DEFINE output:format '_JAVA_'
  CONSTRUCT { ?s ?p ?o }
WHERE
  {
    ?s ?p ?o .
    FILTER (?s = iri(?::0))
  }
LIMIT 1