public void setInitialCapacity(int initialCapacity) {
    if (initialCapacity < 0) {
      throw new IllegalArgumentException(
          "initialCapacity must be >= 0");
    }
    regionAttributes.initialCapacity = initialCapacity;
    regionAttributes.setHasInitialCapacity(true);
  }
Sets the entry initial capacity for the next {@code RegionAttributes} created. This value is
used in initializing the map that holds the entries. Default is 16.

@param initialCapacity the initial capacity of the entry map
@throws IllegalArgumentException if initialCapacity is negative.
@see java.util.HashMap
geode-core/src/main/java/org/apache/geode/cache/AttributesFactory.java