GNU Trove

gnu.trove
Class TObjectFloatIterator

java.lang.Object
  |
  +--gnu.trove.TIterator
        |
        +--gnu.trove.TObjectFloatIterator

public class TObjectFloatIterator
extends gnu.trove.TIterator

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.forward();
   if (satisfiesCondition(it.key()) {
     doSomethingWithValue(it.value());
   }
 }
 
 // modifying values in-place through iteration:
 for (TObjectFloatIterator it = map.iterator();
      it.hasNext();) {
   it.forward();
   if (satisfiesCondition(it.key()) {
     it.setValue(newValueForKey(it.key()));
   }
 }
 
 // deleting entries during iteration:
 for (TObjectFloatIterator it = map.iterator();
      it.hasNext();) {
   it.forward();
   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: TObjectFloatIterator.java,v 1.1 2002/09/22 21:53:42 ericdf Exp $
Author:
Eric D. Friedman

Field Summary
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.
 
Constructor Summary
TObjectFloatIterator(TObjectFloatHashMap map)
           
 
Method Summary
 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.
 java.lang.Object 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.

Constructor Detail

TObjectFloatIterator

public TObjectFloatIterator(TObjectFloatHashMap map)
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.

Specified by:
nextIndex in class gnu.trove.TIterator
Returns:
an int value

advance

public void advance()
Moves the iterator forward to the next entry in the underlying map.

Throws:
NoSuchElementException - if the iterator is already exhausted

key

public java.lang.Object 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.


GNU Trove

GNU Trove is copyright 2001-2003 Eric D. Friedman. All Rights Reserved.