### Question:
MutableInt extends Number implements Comparable<MutableInt>, Mutable<Number> { public final int getAndAdd(int delta) { final int oldValue = value; this.value += delta; return oldValue; } MutableInt();  MutableInt(int value);  MutableInt(Number value);  MutableInt(String value); @Override Integer getValue(); @Override void setValue(Number value); void setValue(int value); @Override int compareTo(MutableInt anotherInteger); @Override int intValue(); @Override long longValue(); @Override float floatValue(); @Override double doubleValue(); @Override int hashCode(); @Override boolean equals(Object obj); @Override String toString(); final int getAndIncrement(); final int getAndDecrement(); final int getAndAdd(int delta); final int incrementAndGet(); final int decrementAndGet(); final int addAndGet(int delta);  }### Answer:
@Test public void testGetAndAdd() { MutableInt i = new MutableInt(0); assertTrue(i.getAndAdd(1) == 0); }