Exemple #1
1
  /**
   * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and values themselves are
   * not cloned.
   *
   * @return a shallow copy of this map
   */
  public Object clone() {
    HashMap<K, V> result = null;
    try {
      result = (HashMap<K, V>) super.clone();
    } catch (CloneNotSupportedException e) {
      // assert false;
    }
    result.table = new Entry[table.length];
    result.entrySet = null;
    result.modCount = 0;
    result.size = 0;
    result.init();
    result.putAllForCreate(this);

    return result;
  }
Exemple #2
0
  /**
   * Constructs an empty <tt>HashMap</tt> with the specified initial capacity and load factor.
   *
   * @param initialCapacity the initial capacity
   * @param loadFactor the load factor
   * @throws IllegalArgumentException if the initial capacity is negative or the load factor is
   *     nonpositive
   */
  public HashMap(int initialCapacity, float loadFactor) {
    if (initialCapacity < 0)
      throw new IllegalArgumentException("Illegal initial capacity: " + initialCapacity);
    if (initialCapacity > MAXIMUM_CAPACITY) initialCapacity = MAXIMUM_CAPACITY;
    if (loadFactor <= 0 || Float.isNaN(loadFactor))
      throw new IllegalArgumentException("Illegal load factor: " + loadFactor);

    // Find a power of 2 >= initialCapacity
    int capacity = 1;
    while (capacity < initialCapacity) capacity <<= 1;

    this.loadFactor = loadFactor;
    threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
    table = new Entry[capacity];
    useAltHashing = sun.misc.VM.isBooted() && (capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD);
    init();
  }
Exemple #3
0
  /** Reconstitute the {@code HashMap} instance from a stream (i.e., deserialize it). */
  private void readObject(java.io.ObjectInputStream s) throws IOException, ClassNotFoundException {
    // Read in the threshold (ignored), loadfactor, and any hidden stuff
    s.defaultReadObject();
    if (loadFactor <= 0 || Float.isNaN(loadFactor))
      throw new InvalidObjectException("Illegal load factor: " + loadFactor);

    // set hashSeed (can only happen after VM boot)
    Holder.UNSAFE.putIntVolatile(
        this, Holder.HASHSEED_OFFSET, sun.misc.Hashing.randomHashSeed(this));

    // Read in number of buckets and allocate the bucket array;
    s.readInt(); // ignored

    // Read number of mappings
    int mappings = s.readInt();
    if (mappings < 0) throw new InvalidObjectException("Illegal mappings count: " + mappings);

    int initialCapacity =
        (int)
            Math.min(
                // capacity chosen by number of mappings
                // and desired load (if >= 0.25)
                mappings * Math.min(1 / loadFactor, 4.0f),
                // we have limits...
                HashMap.MAXIMUM_CAPACITY);
    int capacity = 1;
    // find smallest power of two which holds all mappings
    while (capacity < initialCapacity) {
      capacity <<= 1;
    }

    table = new Entry[capacity];
    threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
    useAltHashing = sun.misc.VM.isBooted() && (capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD);

    init(); // Give subclass a chance to do its thing.

    // Read the keys and values, and put the mappings in the HashMap
    for (int i = 0; i < mappings; i++) {
      K key = (K) s.readObject();
      V value = (V) s.readObject();
      putForCreate(key, value);
    }
  }