com.google.common.collect.MultitransformedIterator Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of guava-gwt Show documentation
Show all versions of guava-gwt Show documentation
Guava is a suite of core and expanded libraries that include
utility classes, Google's collections, I/O classes, and
much more.
This project includes GWT-friendly sources.
/*
* Copyright (C) 2016 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.common.collect;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.CollectPreconditions.checkRemove;
import com.google.common.annotations.GwtCompatible;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Similar to {@link TransformedIterator}, this iterator transforms a backing iterator.
* However, rather than enforcing a one-to-one mapping, each element in the backing iterator
* can be transformed into an arbitrary number of elements (i.e. a one-to-many mapping).
*
* @author James Sexton
*/
@GwtCompatible
abstract class MultitransformedIterator implements Iterator {
final Iterator extends F> backingIterator;
private Iterator extends T> current = Iterators.emptyIterator();
private Iterator extends T> removeFrom;
MultitransformedIterator(Iterator extends F> backingIterator) {
this.backingIterator = checkNotNull(backingIterator);
}
abstract Iterator extends T> transform(F from);
@Override
public boolean hasNext() {
checkNotNull(current); // eager for GWT
if (current.hasNext()) {
return true;
}
while (backingIterator.hasNext()) {
// checkNotNull the assignment, so that current is null even if the exception is caught
checkNotNull(current = transform(backingIterator.next()));
if (current.hasNext()) {
return true;
}
}
return false;
}
@Override
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
removeFrom = current;
return current.next();
}
@Override
public void remove() {
checkRemove(removeFrom != null);
removeFrom.remove();
removeFrom = null;
}
}