/guava/android/guava/src/com/google/common/collect/TreeTraverser.java
this.stack = new ArrayDeque<>( ) ;this.queue = new ArrayDeque<T>( ) ;
this.queue = new ArrayDeque<T> ( ) ;
}; } private final class BreadthFirstIterator extends UnmodifiableIterator<T> implements PeekingIterator<T> { private final Queue<T> queue; BreadthFirstIterator(T root) { <extra_id_0> queue.add(root); } @Override public boolean hasNext() { return !queue.isEmpty(); }