package prefuse.data.util;
import java.util.Iterator;
import java.util.NoSuchElementException;
import prefuse.data.Tuple;
import prefuse.data.expression.Predicate;
/**
* Iterator over tuples that filters the output by a given predicate.
*
* @author <a href="http://jheer.org">jeffrey heer</a>
*/
public class FilterIterator implements Iterator {
private Predicate predicate;
private Iterator tuples;
private Tuple next;
/**
* Create a new FilterIterator.
* @param tuples an iterator over tuples
* @param p the filter predicate to use
*/
public FilterIterator(Iterator tuples, Predicate p) {
this.predicate = p;
this.tuples = tuples;
next = advance();
}
private Tuple advance() {
while ( tuples.hasNext() ) {
Tuple t = (Tuple)tuples.next();
if ( predicate.getBoolean(t) ) {
return t;
}
}
tuples = null;
next = null;
return null;
}
/**
* @see java.util.Iterator#next()
*/
public Object next() {
if ( !hasNext() ) {
throw new NoSuchElementException("No more elements");
}
Tuple retval = next;
next = advance();
return retval;
}
/**
* @see java.util.Iterator#hasNext()
*/
public boolean hasNext() {
return ( tuples != null );
}
/**
* Not supported.
* @see java.util.Iterator#remove()
*/
public void remove() {
throw new UnsupportedOperationException();
}
} // end of class FilterIterator