 If entries is full, then this implementation may end up using the entries array
           * directly and writing over the entry objects with non-terminal entries, but this is
           * safe; if this Builder is used further, it will grow the entries array (so it can't
           * affect the original array), and future build() calls will always copy any entry
           * objects that cannot be safely reused.
 If entries is full, then this implementation may end up using the entries array
           * directly and writing over the entry objects with non-terminal entries, but this is
           * safe; if this Builder is used further, it will grow the entries array (so it can't
           * affect the original array), and future build() calls will always copy any entry
           * objects that cannot be safely reused. | ImmutableBiMap.java