FIM.Util
Class FilterIterator

java.lang.Object
  |
  +--FIM.Util.FilterIterator

All Implemented Interfaces:

Iterator

public abstract class FilterIterator

extends Object

implements Iterator

An iterator of objects matching a certain criteria. It is based on another iterator from which only elements will be returned, which match certain criteria. Subclasses must implement the actual filtering function protected boolean matchesFilter(Object toTest). The remove method can only be called between next and hasNext (After hasNext was called removal is no longer possible as the underlying iterator is at another position already).

Version:

1.0, 1.7.2000

Author:

Michael Sonntag

Constructor Summary

protected

FilterIterator() Creates a new iterator for filtering another iterator.

Method Summary

boolean	hasNext() Returns true if the iteration has more elements.
protected abstract boolean	matchesFilter(Object toTest) The function implementing the filtering function.
Object	next() Returns the next matching element of this iterator.
void	remove() Removes from the underlying collection the last element returned by the iterator.
protected void	setBaseIterator(Iterator fullIter) Sets the iterator for filtering objects from another iterator.

Methods inherited from class java.lang.Object

, clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FilterIterator

protected FilterIterator()

Creates a new iterator for filtering another iterator.

Method Detail

setBaseIterator

protected void setBaseIterator(Iterator fullIter)

Sets the iterator for filtering objects from another iterator.
The filtering parameters of the subclass must be set when this function is called. Calls to matchesFilter(Object toTest) must be possible!

Parameters:

fullIter - the iterator of all elements which will be filtered

Throws:

IllegalArgumentException - if the parameter is null

IllegalStateException - if the base iterator is already set

hasNext

public boolean hasNext()

Returns true if the iteration has more elements. (In other words, returns true if next would return an element rather than throwing an exception.)

Specified by:

hasNext in interface Iterator

Returns:

true if this iterator has more matching elements; false otherwise

Throws:

IllegalStateException - if the base iterator is not set

next

public Object next()

Returns the next matching element of this iterator.

Specified by:

next in interface Iterator

Returns:

the next matching element of this iterator

Throws:

NoSuchElementException - if no more matching elements exist

IllegalStateException - if the base iterator is not set

matchesFilter

protected abstract boolean matchesFilter(Object toTest)

The function implementing the filtering function.

Parameters:

totest - the object to test if it matches the filter

Returns:

true if the element should be returned; false if this element does not match the criteria and should be suppressed

remove

public void remove()

Removes from the underlying collection the last element returned by the iterator. This method can be called only once per call to next. The behavior is unspecified if the underlying collection is modified while the iteration is in progress in any way other than by calling this method. If hasNext is called after next, this will throw a IllegalStateException: We must move on at least one object to see if it matches the criteria before we can tell the user whether at least one more matching element exists. Therefore in the underlying iterator we are at a different object and cannot anymore remove the last by us returned object.

Specified by:

remove in interface Iterator

Throws:

IllegalStateException - if the base iterator is not set or if the next method has not yet been called, or the remove method has already been called after the last call to the next method.