Oracle Java 1Z0-830 glossary of Java 21 language, flow, collections, modules, and concurrency terms.
Keep this glossary nearby when Java 21 terms start to blend together. The exam punishes fuzzy vocabulary because fuzzy vocabulary usually hides fuzzy reasoning.
Automatic conversion between a primitive and its wrapper type such as int and Integer.
The order elements are seen while iterating or streaming, which can affect results for ordered operations.
Compile-time removal of most generic type information from runtime class metadata.
An interface with one abstract method, suitable for lambda expressions and method references.
A restriction such as extends or super that limits what types are legal in a generic context.
A concurrency ordering rule that determines when one thread’s writes are guaranteed visible to another.
Unable to change after construction. Strings and records are common exam examples, though records can still hold mutable components.
Java syntax that combines a type check with variable binding, such as instanceof patterns and pattern-aware switch.
Short rule for wildcard direction: producer extends, consumer super.
Concise Java type for modeling data with generated constructor, accessors, equals, hashCode, and toString.
Localization mechanism that stores locale-specific messages and text resources.
Class or interface that explicitly restricts which other types may extend or implement it.
Java 21 collection family concept that exposes well-defined first and last style operations and encounter order.
A chain of stream operations that stays lazy until a terminal operation runs.
The stream operation that actually triggers evaluation, such as collect, count, or forEach.
Statement form that closes declared resources automatically, typically in reverse declaration order.
Collection view or factory result that rejects structural modification attempts.
Lightweight thread model in Java designed for large numbers of concurrent blocking tasks.
Generic placeholder type such as ?, ? extends T, or ? super T.
Keyword used to return a value from a block-style switch expression arm.