1Z0-829 Study Guide — How to Pass Oracle Certified Professional Java SE 17 Developer

OCP Java 17 (1Z0-829) is a single exam — there is no longer a prerequisite OCA exam as of the Java 11 certification restructuring. The exam is 50 questions in 90 minutes with a 68% passing score. The question format includes code snippets you must analyse for correctness, output, or compilation errors.

Code that does not compile is a valid exam answer option. Know the difference between a compilation error (incorrect syntax, type mismatch, accessing private member) and a runtime exception (NullPointerException, ClassCastException, ArrayIndexOutOfBoundsException). Read exam code carefully — subtle issues like missing semicolons or incorrect generic types often hide in the options.

var (local variable type inference) can only be used for local variables (not fields, parameters, or return types), must be initialised at declaration, and cannot be initialised to null without a cast. Know the contexts where var is and is not allowed — the exam regularly presents var in invalid contexts as a distractor.

The Collections framework hierarchy is tested: Iterable → Collection → List/Set/Queue; Map is separate. Know the concrete implementations: ArrayList (resizable array, fast random access), LinkedList (doubly-linked, fast insert/delete), HashSet (no order, no duplicates), LinkedHashSet (insertion order, no duplicates), TreeSet (sorted, no duplicates), HashMap, LinkedHashMap, TreeMap.

Concurrent programming on OCP Java 17: know Runnable vs Callable (Callable returns a value and can throw checked exceptions), ExecutorService lifecycle (submit, shutdown, awaitTermination), synchronized methods/blocks, volatile keyword, and atomic classes (AtomicInteger, AtomicBoolean). Also know the difference between a thread-safe class and a class used safely by one thread at a time.