How to Efficiently Convert an int[] Array to a List in Java?

Effective Conversion of int[] to List in Java

When faced with the need to convert an int[] array to a List in Java, a common approach involves iterating through each element and assigning it to the resulting list. However, Java offers more efficient solutions to this problem, particularly for Java 8 and above users.

Java 8 Stream-Based Solution

Java 8 introduced streams, which provide a powerful mechanism for data transformation. Using streams, you can achieve the conversion using the following steps:

1. Create a stream of your int array: Use the Arrays.stream() or IntStream.of() method to create a stream from your int array.
2. Boxed conversion: Apply the IntStream#boxed method to convert primitive int values to Integer objects.
3. Collection into a list: Finally, use the Stream.collect(Collectors.toList()) method (or Stream#toList() in Java 16 ) to collect the boxed elements into a list.

Example:

int[] ints = {1,2,3};
List<Integer> list = Arrays.stream(ints).boxed().collect(Collectors.toList());

Other Solutions

While the stream-based solution is highly efficient in Java 8 and above, there are alternative methods for earlier Java versions:

• Java 7 and below: Use the Arrays.asList(int... values) method, keeping in mind its limitations (it creates an immutable list and performs boxing internally).
• Apache Commons Lang3: Utilize the CollectionUtils.toList() method, which handles primitive arrays more efficiently (but may still require boxing).

By understanding the various methods available, you can choose the most appropriate solution for your specific Java environment and requirements.

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