How Can I Iterate Through a Java 8 Stream While Accessing Element Indices?

Iterating a Stream with Indices in Java 8: A Concise Solution

To effectively iterate over a stream and access indices, several approaches are available.

Using a Stream of Indices

The cleanest solution is to create a stream of indices and filter it based on the stream's elements:

String[] names = {"Sam", "Pamela", "Dave", "Pascal", "Erik"};
IntStream.range(0, names.length)
         .filter(i -> names[i].length() <= i)
         .mapToObj(i -> names[i])
         .collect(Collectors.toList());

This approach ensures that the resulting list only contains elements that meet the index-based criterion.

Using an AtomicInteger Counter

Another alternative is to maintain a mutable counter within the stream:

String[] names = {"Sam", "Pamela", "Dave", "Pascal", "Erik"};
AtomicInteger index = new AtomicInteger();
List<String> list = Arrays.stream(names)
                          .filter(n -> n.length() <= index.incrementAndGet())
                          .collect(Collectors.toList());

This method provides a familiar syntax similar to for loops. However, it's crucial to note that this approach can potentially break when used on a parallel stream as items may not be processed in order.

Ultimately, the choice of approach depends on the specific requirements and performance considerations of the application.

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