android/guava/src/com/google/common/collect/Iterators.java
@Beta
  public static <T> UnmodifiableIterator<T> mergeSorted(
      Iterable<? extends Iterator<? extends T>> iterators, Comparator<? super T> comparator) {
    checkNotNull(iterators, "iterators");
    checkNotNull(comparator, "comparator");

    return new MergingIterator<T>(iterators, comparator);
  }
@Beta
  public static <T> UnmodifiableIterator<T> mergeSorted(
      Iterable<? extends Iterator<? extends T>> iterators, Comparator<? super T> comparator) {
    checkNotNull(iterators, "iterators");
    checkNotNull(comparator, "comparator");

    return new MergingIterator<T>(iterators, comparator);
  }
@ Beta public static < T > UnmodifiableIterator < T > mergeSorted ( Iterable < ? extends Iterator < ? extends T > > iterators , Comparator < ? super T > comparator ) { checkNotNull ( iterators , "iterators" ) ; checkNotNull ( comparator , "comparator" ) ; return new MergingIterator < T > ( iterators , comparator ) ; }
Returns an iterator over the merged contents of all given {@code iterators}, traversing every
element of the input iterators. Equivalent entries will not be de-duplicated.

<p>Callers must ensure that the source {@code iterators} are in non-descending order as this
method does not sort its input.

<p>For any equivalent elements across all {@code iterators}, it is undefined which element is
returned first.

@since 11.0
Returns an iterator over the merged contents of all given { @code iterators } traversing every element of the input iterators . Equivalent entries will not be de - duplicated .