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Oracle Certified Professional: Java SE Developer 1Z0-831 (Java SE 25) · Domain 5: Working with arrays and collections

Sequenced collections: getFirst, getLast, addFirst, reversed

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Last reviewed September 25, 2026 · Leer en español

Before Java 21, getting the first or last element worked differently for each collection type: list.get(0) and list.get(list.size() - 1) for lists, deque.getFirst() for deques, sortedSet.first() for sorted sets, and nothing convenient at all for LinkedHashSet. Sequenced collections, added in Java 21, give every collection with a defined encounter order one common set of methods.

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