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Java / Java 21 Collection Framework features Interview questions

What are pollFirstEntry() and pollLastEntry()?

pollFirstEntry() and pollLastEntry() remove and return the first and last entries of a SequencedMap, combining a read and a delete into one call.

LinkedHashMap<String, Integer> queue = new LinkedHashMap<>();
queue.put("job1", 1);
queue.put("job2", 2);
Map.Entry<String, Integer> next = queue.pollFirstEntry(); // job1=1, removed

Unlike firstEntry()/lastEntry(), these mutate the map. They also return null rather than throwing when the map is empty, which makes them convenient for drain-until-empty loops.

pollFirstEntry() differs from firstEntry() because it:
Calling pollLastEntry() on an empty map returns:

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