How Can I Flatten a List of Lists into a Single List in Java 8?

Converting List of Lists to List in Java 8

When working with nested lists, it can be useful to flatten them into a single, linear list for easier iteration and processing. Java 8 offers several methods that can accomplish this task.

One effective approach is using the flatMap operation. Let's assume we have a List> named list that we want to flatten. The following code demonstrates how to achieve this:

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

List<List<Object>> list = ...

List<Object> flat = list.stream()
    .flatMap(Stream::of)
    .collect(Collectors.toList());

flatMap takes each element in the list, which is another list of Objects, and converts it into a stream. The individual objects from each sublist are then merged into a single stream. Finally, we convert this flattened stream back into a list using Collectors.toList().

This solution leverages the power of streams to simplify complex data manipulation tasks. By using flatMap, we can easily unroll nested lists into a single, linear representation.

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