How to Add Elements to a List Created with Arrays.asList() in Java

How can I add new elements to a List created with Arrays.asList() in Java without deleting the previous elements?

List<String> myList = new ArrayList<>(Arrays.asList("A", "B", "C")); // Convert to ArrayList
myList.add("D"); // Adding new element
System.out.println(myList); // Output: [A, B, C, D]

In Java, when you use `Arrays.asList()`, it returns a fixed-size list backed by the specified array. Therefore, operations like `add()` or `addAll()` will throw an `UnsupportedOperationException`. If you need to add elements, you should create a new instance of a List that is not fixed-size, like an `ArrayList`.

List<String> myList = new ArrayList<>(Arrays.asList("A", "B", "C")); // Convert to ArrayList
myList.add("D"); // Now you can add new elements
System.out.println(myList); // Output will be: [A, B, C, D]

Causes

• `Arrays.asList()` creates a fixed-size list which doesn't support adding new elements.
• The original array's size cannot be modified after the list is created.

Solutions

• Convert the fixed-size list from `Arrays.asList()` into an `ArrayList`, which allows dynamic resizing; use `new ArrayList<>(Arrays.asList(...))`.
• Use `Collections.addAll()` to add elements to an `ArrayList`.
• Consider using a different data structure if frequent additions are needed.

Mistake: Attempting to directly add elements to the list from `Arrays.asList()`.

Solution: Create a new `ArrayList` from the output of `Arrays.asList()`, and then add elements.

Mistake: Not using a mutable collection when planning to add or remove elements.

Solution: Always use collections like `ArrayList` when you need a dynamic size.