gnu.trove

Class TIntObjectIterator

java.lang.Object

gnu.trove.TIntObjectIterator

public class TIntObjectIterator
extends Object

Iterator for maps of type int and Object.

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 (TIntObjectIterator it = map.iterator();
      it.hasNext();) {
   it.forward();
   if (satisfiesCondition(it.key()) {
     doSomethingWithValue(it.value());
   }
 }
 

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

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

 // faster iteration by avoiding hasNext():
 TIntObjectIterator iterator = map.iterator();
 for (int i = map.size(); i-- > 0;) {    
   iterator.advance();     
   doSomethingWithKeyAndValue(iterator.key(), iterator.value());
 }   
 

Version:

$Id: TIntObjectIterator.java,v 1.3 2004/11/24 20:00:00 casutton Exp $

Author:

Eric D. Friedman

Field Summary

Fields

Modifier and Type	Field and Description
protected int	_expectedSize the number of elements this iterator believes are in the data structure it accesses.
protected TPrimitiveHash	_hash the collection on which this iterator operates.
protected int	_index the index used for iteration.

Constructor Summary

Constructors

Constructor and Description
TIntObjectIterator(TIntObjectHashMap map) Creates an iterator over the specified map

Method Summary

Modifier and Type	Method and 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.
int	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.
Object	setValue(Object val) Replace the value of the mapping at the iterator's position with the specified value.
Object	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 TPrimitiveHash _hash

the collection on which this iterator operates.

_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

TIntObjectIterator

public TIntObjectIterator(TIntObjectHashMap map)

Creates an iterator over the specified 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 int 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 Object 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 Object setValue(Object 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.

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

Throws:

ConcurrentModificationException - if the underlying collection's size has been modified since the iterator was created.

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.