public static <T> void setCollection(final ObjectNode node, final String fieldName, final Collection<T> coll, final Func1<T, JsonNode> mapper) {
        set(node, fieldName, fromCollection(coll, mapper));
    }
constructs a boolean value from a node. If node is null or not boolean, defaultValue is returned.
main/src/main/java/cgeo/geocaching/utils/JsonUtils.java