How Can I Efficiently Combine Two Lists in Java?

Joining Two Lists in Java Efficiently

Combining multiple lists into a single collection is a common task in Java. While the provided code segment using addAll() is functional, it involves creating a new list and iterating over both original lists, which can be inefficient for large datasets.

Java 8 and Later:

For Java 8 and subsequent versions, a more concise and efficient approach is leveraging Java streams:

List<String> newList = Stream.concat(listOne.stream(), listTwo.stream())
                             .collect(Collectors.toList());

This code creates a new stream by concatenating the streams of both lists and collects the elements into a new list named newList. It preserves the original lists and performs the operation lazily, minimizing memory consumption and improving performance.

Java 16 and Later:

In Java 16 and later, a simplified version of the stream-based solution can be used:

List<String> newList = Stream.concat(listOne.stream(), listTwo.stream()).toList();

This code utilizes the toList() method introduced in Java 16, which creates a new list directly from the stream without the need for an explicit collector.

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