gnu.trove

Class TObjectIntIterator

public class TObjectIntIterator extends TIterator

Iterator for maps of type Object and int.

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 (TObjectIntIterator it = map.iterator();
      it.hasNext();) {
   it.forward();
   if (satisfiesCondition(it.key()) {
     doSomethingWithValue(it.value());
   }
 }
 
 // modifying values in-place through iteration:
 for (TObjectIntIterator it = map.iterator();
      it.hasNext();) {
   it.forward();
   if (satisfiesCondition(it.key()) {
     it.setValue(newValueForKey(it.key()));
   }
 }
 
 // deleting entries during iteration:
 for (TObjectIntIterator it = map.iterator();
      it.hasNext();) {
   it.forward();
   if (satisfiesCondition(it.key()) {
     it.remove();
   }
 }
 
 // faster iteration by avoiding hasNext():
 TObjectIntIterator iterator = map.iterator();
 for (int i = map.size(); i-- > 0;) {
   iterator.advance();
   doSomethingWithKeyAndValue(iterator.key(), iterator.value());
 }
 

Version: $Id: TObjectIntIterator.java,v 1.1 2002/09/22 21:53:42 ericdf Exp $

Author: Eric D. Friedman

Field Summary
TObjectIntHashMap_map
Constructor Summary
TObjectIntIterator(TObjectIntHashMap map)
Method Summary
voidadvance()
Moves the iterator forward to the next entry in the underlying map.
Objectkey()
Provides access to the key of the mapping at the iterator's position.
protected intnextIndex()
Returns the index of the next value in the data structure or a negative value if the iterator is exhausted.
intsetValue(int val)
Replace the value of the mapping at the iterator's position with the specified value.
intvalue()
Provides access to the value of the mapping at the iterator's position.

Field Detail

_map

private final TObjectIntHashMap _map

Constructor Detail

TObjectIntIterator

public TObjectIntIterator(TObjectIntHashMap map)

Method Detail

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 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.

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 int value

setValue

public int setValue(int 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.

value

public int 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.