java-oo-design

Use when Java code reads serialized objects - ObjectInputStream, readObject/readResolve, Serializable types crossing a trust boundary, Jackson polymorphic…

Use when deciding how a Java failure travels - catch(Exception), empty catch blocks, log-and-throw, wrapping and rethrowing, return inside finally, validation…

Use when audit or other cross-cutting logging is written inside Spring business methods - repeated SecurityContextHolder plus log.info blocks, or when…

Use when building test fixtures in Java - noisy ArrayList setup, List.of vs Arrays.asList, generating realistic data with Datafaker/JavaFaker or Instancio, or…

Use when Java generics fight back - a List<Subtype> rejected by a List<Supertype> parameter, wildcards (?

Use when a Java application leaks memory, resources or throughput - OutOfMemoryError after days of uptime, a connection pool that drains, AutoCloseable…

Use when overriding equals, hashCode, toString or compareTo in Java - an object missing from a HashSet, contains() returning false, Lombok @Data on an entity…

Use when writing or reviewing Java lambdas, streams or functional interfaces - stream vs loop, Predicate/Function/Supplier/Consumer choice, declaring a…

Use when Java code is shared across threads or runs asynchronously - check-then-act or get-modify-put on a shared map, lost updates, blocking get()/join() in…

Use when modeling with Java enums - wanting to extend or subclass one, sharing behavior between enums, state transitions, sets of enum constants, permissions…