guava/src/com/google/common/collect/Multisets.java
static <E> boolean setCountImpl(Multiset<E> self, E element, int oldCount, int newCount) {
    checkNonnegative(oldCount, "oldCount");
    checkNonnegative(newCount, "newCount");

    if (self.count(element) == oldCount) {
      self.setCount(element, newCount);
      return true;
    } else {
      return false;
    }
  }
static <E> boolean setCountImpl(Multiset<E> self, E element, int oldCount, int newCount) {
    checkNonnegative(oldCount, "oldCount");
    checkNonnegative(newCount, "newCount");

    if (self.count(element) == oldCount) {
      self.setCount(element, newCount);
      return true;
    } else {
      return false;
    }
  }
An implementation of {@link Multiset#setCount(Object, int, int)}.