book

Java Generics and Collections, 2nd Edition

by Maurice Naftalin, Philip Wadler

June 2025

Intermediate to advanced

368 pages

10h 7m

English

O'Reilly Media, Inc.

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Preface
Acknowledgments for the Second EditionIntended AudienceObtaining the Example ProgramsConventions Used in This BookAssertionsO’Reilly Online LearningHow to Contact UsPreface to the First EditionAcknowledgments for the First Edition
I. Generics
1. Introduction
Generic TypesGenerics Versus TemplatesGeneric Methods and VarargsPrimitive and Reference TypesConclusion
2. Subtyping and Wildcards
Subtyping and the Substitution PrincipleWildcardsWildcards with extendsWildcards with superThe Get and Put PrincipleArraysBounded or Unbounded?Using an Unbounded WildcardUsing a Bounded WildcardWildcard CaptureRestrictions on WildcardsInstance CreationGeneric Method CallsSupertypesConclusion
3. Comparison and Bounds
ComparableThe Contract for ComparableConsistent with equalsComparing Integral ValuesThe Maximum of a CollectionA Fruity ExampleComparatorComparator MethodsEnumerated TypesMultiple BoundsBridge MethodsCovariant OverridingConclusion
4. Declarations
ConstructorsStatic MembersNested ClassesHow Erasure WorksConclusion
5. Reifiable and Nonreifiable Types
Reifiable TypesInstance Tests and CastsUnchecked CastsException HandlingGenerics and ArraysGeneric Array CreationThe Principle of Truth in AdvertisingHow to Create ArraysArray Begets ArrayA Classy AlternativeHow to Define ArrayListThe Principle of Indecent ExposureArray Creation and VarargsWhere Reifiable Types Are RequiredOn the Design of Java GenericsErasureUnbounded WildcardsArraysArrays::copyOfConclusion
6. Reflection
Generics for ReflectionReflected Types Are Reifiable TypesReflection for Primitive TypesA Generic Reflection LibraryReflection for GenericsReflecting Generic TypesConclusion
7. Effective Generics
Eliminate Unchecked WarningsEnforce Type Safety When Calling Untrusted CodeSpecialize to Create Reifiable TypesAvoid Single-Use Type VariablesUse Generic Helper Methods to Capture a WildcardCast Through Raw Types When NecessaryUse Generic Array Types with CareUse Type Tokens for Run-Time Type InformationConclusion
II. Collections

8. The Main Interfaces of the Java Collections Framework
Using the Different Collection TypesSetListMapSequencedMapQueueSequenced CollectionsSequencedCollectionSequencedSet and NavigableSetDequeSequencedMap and NavigableMapConclusion
9. Preliminaries
Iterable and IteratorsImplementationsViewsPerformanceMemoryInstruction Count and the O-notationImmutability and UnmodifiabilityContractsContent-Based OrganizationLambdas and StreamsParallel StreamsCollections and Thread SafetySynchronization and the Legacy CollectionsSynchronized Collections and Fail-Fast IteratorsConcurrent CollectionsConclusion
10. The Collection Interface
The Methods of CollectionAdding ElementsRemoving ElementsQuerying the Contents of a CollectionMaking a Collection’s Contents Available for Further ProcessingUsing the Methods of CollectionAdding ElementsRemoving ElementsQuerying the Contents of a CollectionMaking a Collection’s Contents Available for Further ProcessingImplementing CollectionCollection ConstructorsConclusion
11. The SequencedCollection Interface
The Methods of SequencedCollectionAdding ElementsInspecting ElementsRemoving ElementsGenerating a Reversed ViewConclusion
12. Sets
Defining a Set: Equivalence RelationsSet ImplementationsHashSetCopyOnWriteArraySetEnumSetUnmodifiableSetSet Views of MapsSequencedSetLinkedHashSetNavigableSetThe Methods of NavigableSetTreeSetConcurrentSkipListSetComparing Set ImplementationsConclusion
13. Queues
Queue Interface MethodsAdding an Element to a QueueRetrieving an Element from a QueueUsing the Methods of QueueQueue ImplementationsPriorityQueueConcurrentLinkedQueueBlockingQueueThe Methods of BlockingQueueUsing the Methods of BlockingQueueBlockingQueue ImplementationsTransferQueueDequeThe Methods of DequeDeque ImplementationsBlockingDequeComparing Queue ImplementationsConclusion
14. Lists
List Interface MethodsPositional Access MethodsSearch MethodsView-Generating MethodsList Iteration MethodsMethods Inherited from SequencedCollectionFactory MethodsUsing the Methods of ListUsing Range-View and Iterator MethodsList ImplementationsArrayListLinkedListCopyOnWriteArrayListUnmodifiableListComparing List ImplementationsConclusion
15. Maps
Map Interface MethodsIterable-like OperationsCollection-like OperationsProviding Collection Views of the Keys, Values, or EntriesCompound OperationsFactory MethodsThe Interface Map.EntryUsing the Methods of MapMap ImplementationsHashMapWeakHashMapIdentityHashMapEnumMapUnmodifiableMapSequencedMapThe Methods of SequencedMapLinkedHashMapNavigableMapRetrieving the ComparatorGetting Range ViewsGetting Closest MatchesOther ViewsTreeMapConcurrentMapConcurrentHashMapConcurrentNavigableMapConcurrentSkipListMapComparing Map ImplementationsConclusion
16. The Collections Class
Generic AlgorithmsChanging the Order of List ElementsChanging the Contents of a ListFinding Extreme Values in a CollectionFinding Specific Values in a ListCollection FactoriesWrappersSynchronized CollectionsUnmodifiable CollectionsChecked CollectionsOther MethodsConclusion
17. Guidance for Using the Java Collections Framework
Avoid Anemic Domain ModelsRespect the ‘Ownership’ of CollectionsPrefer Immutable Objects as Set Elements or Map KeysBalance Client and Library Interests in API DesignExploit the Features of RecordsPrefer Records to Parallel ListsUse Records as Composite KeysManage the Mutability of RecordsAvoid Legacy ImplementationsAvoid Synchronized Wrapper CollectionsAvoid LinkedListCustomize Collections Using the Abstract ClassesConclusion
18. Design Retrospective
Fundamental Issues in the Collections Framework DesignDesirable Characteristics of a Collections FrameworkUnmodifiability via SubtypingLimitations of SubtypingComplementing Static TypingLumping and SplittingSummarynullsInconsistent with equalsObject Versus EConcurrent Modification
Afterword
Bibliography
Index
About the Authors

Content preview from Java Generics and Collections, 2nd Edition

About the Authors

Maurice Naftalin has over 50 years’ experience in IT as a developer, designer, architect, manager, teacher, and author. He has been using and teaching Java since JDK 1.0. He is a Java Champion, the author of Mastering Lambdas (2015), and a frequent presenter at conferences worldwide. He disorganizes the annual Java unconference JAlba.

Philip Wadler is professor of theoretical computer science at the University of Edinburgh, Scotland, where his research focuses on functional and logic programming, and the design of programming languages. He was a principal designer of the Haskell programming language, and a codesigner of GJ, work that became the basis for Java generics. Professor Wadler received his PhD in computer science from Carnegie-Mellon.

Stuart Marks is the JDK Core Libraries project lead in the Java Platform Group at Oracle. He is currently the maintainer of the Java Collections Framework. As his alter ego “Dr Deprecator,” he also works on Java’s deprecation mechanism. He has over 30 years of software platform product development experience in the areas of window systems, interactive graphics, and mobile and embedded systems. He holds a master’s degree in computer science from Stanford University.

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Java Generics and Collections, 2nd Edition

by Maurice Naftalin, Philip Wadler

About the Authors

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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