Java Course Glossary

Java Course Glossary

A comprehensive guide to modern Java terminology, syntax, and concepts.

A

Annotation Interface

A specialized interface used to define annotations. Declared using the @interface keyword.

AQS (AbstractQueuedSynchronizer)

A framework for implementing blocking locks and related synchronizers (semaphores, events, etc.) that rely on first-in-first-out (FIFO) wait queues.

Architecture Testing

Testing to ensure code adheres to architectural rules (e.g., layers, naming). Architecture Testing

ArchUnit

A library for checking the architecture of Java code using any plain Java unit test framework. ArchUnit

Assertion

A statement that a predicate (Boolean-valued function) is true at that point in code execution. Assertion

Assumption

A condition that must be met for a test to be meaningful. If an assumption fails, the test is aborted (skipped), not failed. Assumption

C

CAS (Compare-And-Swap)

A CPU instruction used to achieve synchronization without locks. It updates a variable only if it has the expected value, enabling non-blocking algorithms. CAS

Collector

A utility class (java.util.stream.Collectors) that provides implementations for the Stream.collect operation, such as accumulating elements into a list, set, or map. Collector

Compact Constructor

A special constructor in a Record that allows validation or normalization of parameters without repeating the parameter list or assignment logic. Compact Constructor

CompletableFuture

A class that implements Future and CompletionStage, enabling asynchronous, non-blocking programming pipelines. CompletableFuture

Consumer

A functional interface (java.util.function.Consumer<T>) that accepts a single input argument and returns no result. Commonly used in forEach operations. Consumer

D

Deadlock

A situation where two or more threads are blocked forever, each waiting for the other to release a resource.

Dynamic Test

A test generated at runtime by a factory method, allowing for flexible test scenarios. Dynamic Test

E

Effectively Final

A variable or parameter whose value is never changed after it is initialized. Local variables referenced from a lambda expression or anonymous inner class must be effectively final. Effectively Final

Extension Model

The mechanism in JUnit 5 (Jupiter) to extend the framework’s behavior (e.g., callbacks, parameter resolution). Extension Model

F

ForkJoinPool

An ExecutorService for running ForkJoinTasks. It employs a work-stealing algorithm and is the default thread pool used by parallel streams. ForkJoinPool

Function

A functional interface (java.util.function.Function<T, R>) that accepts one argument and produces a result. Commonly used in map operations. Function

Functional Interface

An interface with exactly one abstract method, which can be implemented using a Lambda Expression. Marked with @FunctionalInterface.

I

Immutable

An object whose state cannot be modified after it is created. Records are immutable by default.

Integration Test

A level of software testing where individual units are combined and tested as a group. Integration Test

Intermediate Operation

An operation on a stream (like filter, map) that returns a new stream. These operations are lazy and are not executed until a terminal operation is invoked. Intermediate Operation

J

JUnit

A unit testing framework for the Java programming language. JUnit

L

Lambda Expression

A concise way to represent an instance of a functional interface. It provides a clear and compact syntax for writing anonymous methods. Lambda Expression

Livelock

A condition where threads are not blocked but are too busy responding to each other to make progress.

M

Method Reference

A shorthand syntax (::) for a lambda expression that executes just one existing method. Method Reference

P

Parameterized Test

A test method that is executed multiple times with different arguments. Parameterized Test

Pattern Matching

A mechanism to check if an object has a specific structure and extract data from it in a single operation. Available for instanceof, switch, and Records. Pattern Matching

Permitted Subclass

A class explicitly authorized to extend a Sealed Class using the permits clause.

Pipeline

A sequence of aggregate operations on a data source. A stream pipeline consists of a source, zero or more intermediate operations, and a terminal operation. Pipeline

Predicate

A functional interface (java.util.function.Predicate<T>) that accepts one argument and returns a boolean. Commonly used in filter operations. Predicate

R

ReadWriteLock

A lock that maintains a pair of associated locks, one for read-only operations and one for writing. The read lock may be held simultaneously by multiple reader threads, so long as there are no writers.

Record

A concise class declaration for immutable data carriers. Automatically generates equals, hashCode, toString, and accessors. Record

Record Pattern

A pattern that matches a record type and deconstructs it into its component values.

Reducer

An operation that combines a sequence of elements into a single result by repeated application of a combining operation (e.g., sum, max). Reducer

ReentrantLock

A mutual exclusion lock with the same basic behavior as the implicit monitor lock accessed using synchronized methods and statements, but with extended capabilities (like fairness and interruptibility).

S

Sealed Class

A class or interface that restricts which other classes or interfaces may extend or implement it. Defined using the sealed modifier. Sealed Class

StampedLock

A capability-based lock with three modes for controlling read/write access. It provides an optimistic read mode that is very efficient for read-heavy workloads. StampedLock

Stream

A sequence of elements supporting sequential and parallel aggregate operations. Streams do not store data; they convey data from a source through a pipeline of computational operations. Stream

Supplier

A functional interface (java.util.function.Supplier<T>) that takes no arguments and returns a result. Supplier

Switch Expression

A switch construct that evaluates to a value and can be assigned to a variable. Uses the yield keyword (or arrow syntax) to return values. Switch Expression

T

Terminal Operation

An operation on a stream (like forEach, collect, reduce) that produces a result or a side-effect. Invoking a terminal operation traverses the stream pipeline and consumes the stream. Terminal Operation

Testcontainers

A Java library that supports JUnit tests, providing lightweight, throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container. Testcontainers

Text Block

A multi-line string literal in Java, delimited by triple quotes """, that preserves formatting and eliminates the need for most escape sequences.

U

Unit Test

A type of software testing where individual units or components of a software are tested. Unit Test

V

Var

A reserved type name for local variable type inference. The compiler infers the type of the variable from the initializer.

Virtual Thread

A lightweight thread implementation provided by the JVM (Project Loom) that maps many virtual threads to a small number of carrier OS threads, enabling high-concurrency applications.

W

Work-Stealing

An algorithm used by ForkJoinPool where idle threads “steal” tasks from the deque of busy threads to ensure efficient CPU utilization.

Y

Yield

A context-sensitive keyword used in Switch Expressions to return a value from a case block (similar to return in a method).