Package gnu.trove

Class TObjectFloatIterator<K>


  • public class TObjectFloatIterator<K>
    extends java.lang.Object
    Iterator for maps of type Object and float.

    The iterator semantics for Trove's primitive maps is slightly different from those defined in java.util.Iterator, but still well within the scope of the pattern, as defined by Gamma, et al.

    This iterator does not implicitly advance to the next entry when the value at the current position is retrieved. Rather, you must explicitly ask the iterator to advance() and then retrieve either the key(), the value() or both. This is done so that you have the option, but not the obligation, to retrieve keys and/or values as your application requires, and without introducing wrapper objects that would carry both. As the iteration is stateful, access to the key/value parts of the current map entry happens in constant time.

    In practice, the iterator is akin to a "search finger" that you move from position to position. Read or write operations affect the current entry only and do not assume responsibility for moving the finger.

    Here are some sample scenarios for this class of iterator:

     // accessing keys/values through an iterator:
     for (TObjectFloatIterator it = map.iterator();
          it.hasNext();) {
       it.advance();
       if (satisfiesCondition(it.key()) {
         doSomethingWithValue(it.value());
       }
     }
     

     // modifying values in-place through iteration:
     for (TObjectFloatIterator it = map.iterator();
          it.hasNext();) {
       it.advance();
       if (satisfiesCondition(it.key()) {
         it.setValue(newValueForKey(it.key()));
       }
     }
     

     // deleting entries during iteration:
     for (TObjectFloatIterator it = map.iterator();
          it.hasNext();) {
       it.advance();
       if (satisfiesCondition(it.key()) {
         it.remove();
       }
     }
     

     // faster iteration by avoiding hasNext():
     TObjectFloatIterator iterator = map.iterator();
     for (int i = map.size(); i-- > 0;) {
       iterator.advance();
       doSomethingWithKeyAndValue(iterator.key(), iterator.value());
     }
     
    Version:
    $Id: O2PIterator.template,v 1.3 2007/01/22 16:56:39 robeden Exp $
    Author:
    Eric D. Friedman
    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected int _expectedSize
      the number of elements this iterator believes are in the data structure it accesses.
      protected THash _hash
      the data structure this iterator traverses
      protected int _index
      the index used for iteration.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void advance()
      Moves the iterator forward to the next entry in the underlying map.
      boolean hasNext()
      Returns true if the iterator can be advanced past its current location.
      K key()
      Provides access to the key of the mapping at the iterator's position.
      protected void moveToNextIndex()
      Sets the internal index so that the `next' object can be returned.
      protected int nextIndex()
      Returns the index of the next value in the data structure or a negative value if the iterator is exhausted.
      void remove()
      Removes the last entry returned by the iterator.
      float setValue​(float val)
      Replace the value of the mapping at the iterator's position with the specified value.
      float value()
      Provides access to the value of the mapping at the iterator's position.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • _hash

        protected final THash _hash
        the data structure this iterator traverses
      • _expectedSize

        protected int _expectedSize
        the number of elements this iterator believes are in the data structure it accesses.
      • _index

        protected int _index
        the index used for iteration.
    • Method Detail

      • nextIndex

        protected final int nextIndex()
        Returns the index of the next value in the data structure or a negative value if the iterator is exhausted.
        Returns:
        an float value
      • advance

        public void advance()
        Moves the iterator forward to the next entry in the underlying map.
        Throws:
        java.util.NoSuchElementException - if the iterator is already exhausted
      • key

        public K key()
        Provides access to the key of the mapping at the iterator's position. Note that you must advance() the iterator at least once before invoking this method.
        Returns:
        the key of the entry at the iterator's current position.
      • value

        public float value()
        Provides access to the value of the mapping at the iterator's position. Note that you must advance() the iterator at least once before invoking this method.
        Returns:
        the value of the entry at the iterator's current position.
      • setValue

        public float setValue​(float val)
        Replace the value of the mapping at the iterator's position with the specified value. Note that you must advance() the iterator at least once before invoking this method.
        Parameters:
        val - the value to set in the current entry
        Returns:
        the old value of the entry.
      • hasNext

        public boolean hasNext()
        Returns true if the iterator can be advanced past its current location.
        Returns:
        a boolean value
      • remove

        public void remove()
        Removes the last entry returned by the iterator. Invoking this method more than once for a single entry will leave the underlying data structure in a confused state.
      • moveToNextIndex

        protected final void moveToNextIndex()
        Sets the internal index so that the `next' object can be returned.