@SuppressWarnings("unchecked")
    public <V> ResultTransformer<Map<K, V>> as(Expression<V> expression) {
        final Expression<V> lookup = getLookup(expression);
        return new GroupByMap<K, V>(key, expression) {
            @Override
            protected Map<K, V> transform(Map<K, Group> groups) {
                Map<K, V> results = new LinkedHashMap<K, V>((int) Math.ceil(groups.size() / 0.75), 0.75f);
                for (Map.Entry<K, Group> entry : groups.entrySet()) {
                    results.put(entry.getKey(), entry.getValue().getOne(lookup));
                }
                return results;
            }
        };
    }
Get the results as a map

@param expression projection
@return new result transformer
querydsl-core/src/main/java/com/querydsl/core/group/GroupByBuilder.java