driver-core/src/main/com/mongodb/WriteConcernResult.java
public static WriteConcernResult unacknowledged() {
        return new WriteConcernResult() {
            @Override
            public boolean wasAcknowledged() {
                return false;
            }

            @Override
            public int getCount() {
                throw getUnacknowledgedWriteException();
            }

            @Override
            public boolean isUpdateOfExisting() {
                throw getUnacknowledgedWriteException();
            }

            @Override
            public BsonValue getUpsertedId() {
                throw getUnacknowledgedWriteException();
            }

            @Override
            public boolean equals(final Object o) {
                if (this == o) {
                    return true;
                }
                if (o == null || getClass() != o.getClass()) {
                    return false;
                }

                WriteConcernResult that = (WriteConcernResult) o;
                return !that.wasAcknowledged();
            }

            @Override
            public int hashCode() {
                return 1;
            }

            @Override
            public String toString() {
                return "UnacknowledgedWriteResult{}";
            }

            private UnsupportedOperationException getUnacknowledgedWriteException() {
                return new UnsupportedOperationException("Cannot get information about an unacknowledged write");
            }
        };
    }
public static WriteConcernResult unacknowledged() {
        return new WriteConcernResult() {
            @Override
            public boolean wasAcknowledged() {
                return false;
            }

            @Override
            public int getCount() {
                throw getUnacknowledgedWriteException();
            }

            @Override
            public boolean isUpdateOfExisting() {
                throw getUnacknowledgedWriteException();
            }

            @Override
            public BsonValue getUpsertedId() {
                throw getUnacknowledgedWriteException();
            }

            @Override
            public boolean equals(final Object o) {
                if (this == o) {
                    return true;
                }
                if (o == null || getClass() != o.getClass()) {
                    return false;
                }

                WriteConcernResult that = (WriteConcernResult) o;
                return !that.wasAcknowledged();
            }

            @Override
            public int hashCode() {
                return 1;
            }

            @Override
            public String toString() {
                return "UnacknowledgedWriteResult{}";
            }

            private UnsupportedOperationException getUnacknowledgedWriteException() {
                return new UnsupportedOperationException("Cannot get information about an unacknowledged write");
            }
        };
    }
Create an unacknowledged WriteConcernResult

@return an unacknowledged WriteConcernResult