### Question:
PrimitiveDoubleWrapper extends DoubleWrapper { @Override public boolean isPrimitiveWrapper() { return true; } PrimitiveDoubleWrapper();  PrimitiveDoubleWrapper(double value); @Override void set(Number v); @Override Double getDefault(); @Override boolean isPrimitiveWrapper(); @Override R accept(WrapperVisitor<R, P, Q, TH> visitor, P p, Q q);  }### Answer:
@Test void isPrimitiveWrapper() { PrimitiveDoubleWrapper wrapper = new PrimitiveDoubleWrapper(); assertTrue(wrapper.isPrimitiveWrapper()); }