package com.github.davidmoten.guavamini;
   
   import java.util.Collection;
   import java.util.Collections;
   import java.util.HashSet;
   import java.util.Iterator;
   
   import com.github.davidmoten.guavamini.annotations.VisibleForTesting;
   
  public final class Sets {
  
      private Sets() {
          // prevent instantiation
      }
  
      static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
  
      public static <E> HashSet<E> newHashSet(E... elements) {
          Preconditions.checkNotNull(elements);
          HashSet<E> set = newHashSetWithExpectedSize(elements.length);
          Collections.addAll(set, elements);
          return set;
      }
  
      public static <E> HashSet<E> newHashSetWithExpectedSize(int expectedSize) {
          return new HashSet<E>(capacity(expectedSize));
      }
  
      /**
       * Returns a capacity that is sufficient to keep the map from being resized
       * as long as it grows no larger than expectedSize and the load factor is >=
       * its default (0.75).
       */
      @VisibleForTesting
      static int capacity(int expectedSize) {
          if (expectedSize < 3) {
              checkNonnegative(expectedSize, "expectedSize");
              return expectedSize + 1;
          }
          if (expectedSize < MAX_POWER_OF_TWO) {
              return expectedSize + expectedSize / 3;
          }
          return Integer.MAX_VALUE; // any large value
      }
  
      @VisibleForTesting
      static int checkNonnegative(int value, String name) {
          if (value < 0) {
              throw new IllegalArgumentException(name + " cannot be negative but was: " + value);
          }
          return value;
      }
  
      public static <E> HashSet<E> newHashSet(Iterable<? extends E> elements) {
          return (elements instanceof Collection) ? new HashSet<E>(Collections2.cast(elements))
                  : newHashSet(elements.iterator());
      }
  
      public static <E> HashSet<E> newHashSet(Iterator<? extends E> elements) {
          HashSet<E> set = newHashSet();
          Iterators.addAll(set, elements);
          return set;
      }
  
      public static <E> HashSet<E> newHashSet() {
          return new HashSet<E>();
      }
  
  }