DoubleValueConverter extends AbstractValueConverter<Double> { @Override public String toString(Double value) { if (value == null) { return null; } return String.valueOf(value); } private  DoubleValueConverter(); @Override Double convert(String s); @Override String toString(Double value); static final ValueConverter<Double> INSTANCE; }
@Test public void testToStringNull() throws Exception { assertNull(converter.toString(null)); }