### Question:
StringToDoubleTransformer extends StringToNumberTransformer implements Transformer { @Override public Double apply(Serializable strings) { return tryConvertToNumber(strings).doubleValue(); }  @Override Double apply(Serializable strings);  }### Answer:
@Test void testApply() { Double[] expectedValues = new Double[3]; expectedValues[0] = 0.32435435; expectedValues[1] = 2.5; expectedValues[2] = ((double) 1) / 3; String[] valuesAsStrings = new String[expectedValues.length]; for (int i = 0; i < expectedValues.length; i++) { valuesAsStrings[i] = expectedValues[i].toString(); } Serializable[] transformations = new StringToDoubleTransformer().apply(valuesAsStrings); for (int i = 0; i < valuesAsStrings.length; i++) { assertEquals(expectedValues[i], transformations[i], "of " + i + "th element"); } }