Converting array to list in Java

Converting int[] to List<Integer>

Java 8's Stream API provides an elegant technique to convert int[] to List<Integer>.

int[] intArray = {1, 2, 3};
List<Integer> integerList = Arrays.stream(intArray)
                                  .boxed() // Integers need to wear boxing gloves to become List-compatible
                                  .collect(Collectors.toList());
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Making List modifiable after conversion

Wrap the Arrays.asList() within a new ArrayList<>() to prevent potential UnsupportedOperationException when adding or removing elements.

List<String> modifiableList = new ArrayList<>(Arrays.asList(array)); // Ready for add/remove operations
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Converting int[] to an immutable List<Integer>

For an immutable list, utilize Java 10's List.copyOf() or Java 8's Collectors.toUnmodifiableList().

List<Integer> unmodifiableList = List.copyOf(integerList); // This list is set in stone
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Mind your type! (primitive vs wrapper class)

When using Arrays.asList(), always use the Integer wrapper class array with Arrays.asList() for smooth conversion. Primitive array types may require a manual conversion before use.

Integer[] numbers = {1, 2, 3}; 
List<Integer> numberList = Arrays.asList(numbers); // This is elementary, my dear Watson
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Filling custom collections from arrays

With help from Java Streams, arrays can be collected into various collections like Set, Queue etc.

Set<Integer> set = Arrays.stream(intArray).boxed().collect(Collectors.toSet()); // Who needs duplicate numbers?
Queue<Integer> queue = Arrays.stream(intArray).boxed().collect(Collectors.toCollection(LinkedList::new)); // Queue here for numbers
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Key points to remember

Single-item beta testing: Arrays.asList(int[]) converts the whole array into a single list item.

Mutable or Immutable: Arrays.asList() returns a fixed-size list, i.e., no structural changes (add/remove). For a fully mutable list, resort to new ArrayList<>().

Array wrappers FTW: Arrays.asList(Integer[]) makes a List with each array element becoming a separate List element.

Primitives need a makeover: Avoid direct use of primitive arrays with Arrays.asList(). Instead, pre-convert these into their wrapper-class arrays or use Java 8 Stream operations.

Pro tips for level up

• Leverage IDE features to offload mundane, procedural stuff.
• Consult Effective Java book by Joshua Bloch to understand the nitty-gritty of Arrays.asList().
• To quickly prototype and test : Use online Java environments like IdeOne.com.