List represents an ordered sequence that may contain duplicates. Its content-based equals() comparison requires the other object to implement List and contain equal elements in the same order. section 7.2
Use List carefully around these common boundaries:
- Do not pass a primitive array to Arrays.asList(). Generic varargs inference wraps the entire array as one element, producing a List<int[]> rather than a list of integers; contains(0) therefore returns false. section 2.9.3
- Remember that List.equals() compares content, while wrappers typed only as unmodifiable Collection do not necessarily preserve List equality behavior. section 7.2
- Do not assume every List accepts contains(null). Factory methods such as List.of() reject null search arguments, so guard nullable values before searching. section 8.3
A primitive-array search that never finds zero
For an int[] arr, Arrays.asList(arr).contains(0) searches a one-element list whose element is the original int[] array. Declare intermediate variables explicitly or use a conversion that produces element values. section 2.9.3
static boolean containsZero(int[] arr) {
return Arrays.asList(arr).contains(0);
}
Inspect the compact failure pattern where a primitive array is passed directly to Arrays.asList(). section 2.9.3
List<Integer> list1 = Arrays.asList(1, 2, 3); List<Integer> list2 = Arrays.asList(1, 2, 3); System.out.println(list1.equals(list2)); #1
Compare two Lists with equal elements to see content-based equality in action. section 7.2
Set<String> PLATFORMS = Set.of("PC", "Mac", "Mobile");
Examine the concise factory form whose null-hostile behavior can differ from older unmodifiable collections. section 8.3
