@Override
    protected boolean isNan(Double number) {
        return number.isNaN();
    }
@Test
    void testIsNan() {
        DoubleSummaryAggregator ag = new DoubleSummaryAggregator();
        assertThat(ag.isNan(-1.0)).isFalse();
        assertThat(ag.isNan(0.0)).isFalse();
        assertThat(ag.isNan(23.0)).isFalse();
        assertThat(ag.isNan(Double.MAX_VALUE)).isFalse();
        assertThat(ag.isNan(Double.MIN_VALUE)).isFalse();
        assertThat(ag.isNan(Double.NaN)).isTrue();
    }