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package bjc.data;
import java.util.*;
import java.util.function.Function;
/**
* Create an iterator that applies a flat-map function
*
* @author bjcul
*
* @param <T1> The source type
* @param <T2> The output type
*
*/
public class FlatMapIterator<T1, T2> implements Iterator<T2> {
private Function<T1, Iterator<T2>> action;
private Iterator<T1> source;
private Iterator<T2> output;
/**
* Create a new flat-map iterator
*
* @param source The source iterator
* @param action The action to apply to the iterator
*/
public FlatMapIterator(Iterator<T1> source, Function<T1, Iterator<T2>> action) {
this.source = source;
this.action = action;
}
@Override
public boolean hasNext() {
if (output != null && output.hasNext()) return true;
while (source.hasNext()) {
output = action.apply(source.next());
if (output.hasNext()) return true;
}
return false;
}
@Override
public T2 next() {
if (output != null && output.hasNext()) return output.next();
while (source.hasNext()) {
output = action.apply(source.next());
if (output.hasNext()) return output.next();
}
throw new NoSuchElementException();
}
}
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