guava/src/com/google/common/collect/Multisets.java
public static <E> Multiset.Entry<E> immutableEntry(@Nullable E e, int n) {
    return new ImmutableEntry<E>(e, n);
  }
public static <E> Multiset.Entry<E> immutableEntry(@Nullable E e, int n) {
    return new ImmutableEntry<E>(e, n);
  }
Returns an immutable multiset entry with the specified element and count. The entry will be
serializable if {@code e} is.

@param e the element to be associated with the returned entry
@param n the count to be associated with the returned entry
@throws IllegalArgumentException if {@code n} is negative