Iterator vs ListIterator vs Spliterator in Java (+ Enumeration)
Iterator vs ListIterator vs Spliterator in Java compared in one table, with Enumeration, fail-fast rules, examples and when to use each cursor.
Java Sequenced Collections: getFirst, getLast and reversed()
Learn Java sequenced collections with examples of getFirst(), getLast(), reversed(), putFirst() and the exceptions and upgrade pitfalls to watch for.
Java ConcurrentSkipListMap: Sorted Thread-Safe Map Guide
Java ConcurrentSkipListMap keeps keys sorted for many threads. Learn skip lists, floor and ceiling keys, live range views, polling and TreeMap differences.
Java UnsupportedOperationException: Causes and How to Fix
java.lang.UnsupportedOperationException means the code tried to change a collection that cannot be changed, such as one from Arrays.asList(), List.of() or Collections.unmodifiableMap(). Copy the data into an ArrayList or HashMap to fix it.
Java ArrayDeque Tutorial: Stack, Queue and Deque Examples
Java ArrayDeque tutorial with stack and queue examples, both-end methods, Java 21 reversed(), iteration, an undo history and ArrayDeque vs LinkedList.
Java SynchronousQueue: Direct Handoff Between Threads
Java SynchronousQueue explained with put(), take(), offer() and poll() examples, a producer-consumer handoff, thread pool use and the alternatives.
Java Queue Interface: Methods, Implementations and Examples
Java Queue interface guide with the six methods, how to choose ArrayDeque, PriorityQueue or a BlockingQueue, iteration, BFS and thread-safe queues.
Arrays.asList() vs new ArrayList() in Java: Key Differences
Arrays.asList() vs new ArrayList() in Java explained with examples, covering fixed size, the shared array, List.of(), primitive arrays and conversions.
Java Collections Framework: Hierarchy, Interfaces and Classes
Learn the Java Collections Framework with a Java 21 hierarchy diagram, how to choose List, Set, Map and Queue classes, and links to every tutorial.
Java Nested Map: Create, Update and Iterate a Map of Maps
Create a Java nested map with computeIfAbsent and streams, add, remove and iterate entries, read values safely, deep copy, flatten and choose alternatives.
Java IdentityHashMap: Reference Equality vs HashMap
Java IdentityHashMap compares keys with == instead of equals(). Learn how it differs from HashMap, the String and Integer traps and the Java 20 change.
Java ConcurrentMap: Atomic Methods and Implementations
Java ConcurrentMap with putIfAbsent, compute and merge examples, why get-then-put loses updates, null rules and ConcurrentHashMap vs ConcurrentSkipListMap.
Java CopyOnWriteArraySet: Thread-Safe Set With Examples
Java CopyOnWriteArraySet explained with examples, snapshot iteration, O(n) costs, a chat room use case and a comparison with ConcurrentHashMap.newKeySet().
Java CopyOnWriteArrayList: Snapshot Iterators and Use Cases
Learn how Java CopyOnWriteArrayList copies its array on writes, why its iterators never fail, addIfAbsent(), Java 21 methods and when to use it.
Java TransferQueue and LinkedTransferQueue with Examples
Java TransferQueue and LinkedTransferQueue explained with transfer(), tryTransfer() and put() examples, timeouts, and a comparison with SynchronousQueue.
Java ArrayBlockingQueue: Bounded Blocking Queue Examples
Java ArrayBlockingQueue examples covering put, offer, take, fairness, producer-consumer threads and batch draining with drainTo(), vs LinkedBlockingQueue.
Java PriorityBlockingQueue: Thread-Safe Priority Queue Examples
Java PriorityBlockingQueue examples with Comparator, take(), drainTo() and a print-server worker, plus how it differs from PriorityQueue and DelayQueue.
Java Priority Queue: PriorityQueue, Comparator and Max-Heap
Java priority queue tutorial with PriorityQueue examples for natural order, Comparator, max-heap, equal priorities and top K, and why it prints unsorted.
Java Spliterator: trySplit(), Characteristics and Examples
Java Spliterator examples for tryAdvance(), trySplit(), characteristics and estimateSize(), plus batching, fork/join and a custom Spliterator.
Java TreeMap: Sorted Keys, floorKey(), subMap() and headMap()
Java TreeMap keeps keys sorted in a red-black tree. Learn comparators, floorKey(), ceilingKey(), subMap(), headMap(), tailMap() views and null key rules.
Create a Java List with a Single Element (List.of, singletonList)
Create a Java list with a single element using List.of(), Collections.singletonList(), Arrays.asList() or ArrayList. Mutability and null rules compared.