Common Pitfalls of Arrays.asList in Java
When converting arrays to lists in Java, Arrays.asList cannot handle primitive arrays (treating them as a single element), returns a fixed‑size view that disallows add or remove operations, and shares its backing array so modifications affect both structures, so developers should use boxed streams or copy into a new ArrayList.
Java 8 Stream makes collection operations concise, so developers often convert arrays to List using Arrays.asList . However, this method has three common pitfalls.
It cannot directly convert primitive type arrays. Converting an int[] results in a List with a single element – the whole array – because the array is treated as one object.
The returned List is a fixed-size view backed by the original array; it does not support add or remove operations, leading to UnsupportedOperationException when trying to modify it.
The List shares the underlying array. Changes to the original array are reflected in the List and vice‑versa, which can cause unexpected bugs.
Typical solutions are to use wrapper types (e.g., Integer[] ) for primitive arrays, employ Arrays.stream(...).boxed().collect(Collectors.toList()) , or create a new ArrayList from the view to obtain an independent, mutable list.
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