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package bjc.utils.funcutils;
import java.util.Iterator;
import java.util.function.Function;
/**
* Utility methods for dealing with iterators.
*
* @author bjculkin
*
*/
public class IteratorUtils {
public static class ChainIterator<T1, T2> implements Iterator<T2> {
private Iterator<T1> mainItr;
private Function<T1, Iterator<T2>> trans;
private Iterator<T2> curItr;
public ChainIterator(Iterator<T1> mainItr, Function<T1, Iterator<T2>> trans) {
this.mainItr = mainItr;
this.trans = trans;
}
@Override
public boolean hasNext() {
if (curItr != null) {
if (curItr.hasNext()) return true;
else return mainItr.hasNext();
}
return mainItr.hasNext();
}
@Override
public T2 next() {
if (curItr == null || !curItr.hasNext()) {
curItr = trans.apply(mainItr.next());
}
return curItr.next();
}
}
/**
* Convert an iterator to an iterable.
*
* @param itr
* The iterator to convert.
* @return An iterable that gives back that iterator.
*/
public static <E> Iterable<E> I(Iterator<E> itr) {
return () -> itr;
}
/**
* Convert an iterable to an iterator.
*
* @param itr
* The iterable to convert.
* @return The iterator from that iterable
*/
public static <E> Iterator<E> I(Iterable<E> itr) {
return itr.iterator();
}
public static <A, B> Iterator<B> chain(Iterator<A> itrA, Function<A, Iterator<B>> itrB) {
return new ChainIterator(itrA, itrB);
}
}
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