### Question:
LongWrapper extends AbstractWrapper<Long> implements NumberWrapper<Long> { @Override public void increment() { Long value = doGet(); if (value != null) { doSet(value + 1L); } } LongWrapper();  LongWrapper(Long value); @Override void set(Number v); @Override void increment(); @Override void decrement(); @Override R accept(WrapperVisitor<R, P, Q, TH> visitor, P p, Q q);  }### Answer:
@Test public void testIncrement() { LongWrapper wrapper = new LongWrapper(10L); wrapper.increment(); assertEquals(new Long(11L), wrapper.get()); }