Study 1Z0-831 Java 25 Sealed Types, Interfaces, and Enums: key concepts, common traps, and exam decision cues.
These questions rarely reward intuition. They reward exact hierarchy reading.
| If the stem is mainly about… | Better first instinct |
|---|---|
| restricted subtype set | check sealed and permitted types |
| behavior conflict across interfaces | resolve default-method rules explicitly |
| override legality | check access, static/instance distinction, and return type |
| enum behavior | remember enums are full types, not just constants |
| Trap | Better rule |
|---|---|
| assuming sealed means immutable | sealed restricts subtype relationships, not object mutability |
| treating default methods like free multiple inheritance | conflict rules still apply |
| forgetting static methods are hidden, not overridden | static and instance lanes stay separate |