Table Of ContentMastering Lambdas
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Mastering Lambdas:
Java Programming in
a Multicore World
Maurice Naftalin
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Copyright © 2015 by Maurice Naftalin. All rights reserved. Except as permitted under the United States Copyright Act of 1976, no
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To my boys: Joe, Isaac, Daniel, and Ben
About the Author
MauriceNaftalinhasover30years’experienceinITasadeveloper,designer,archi-
tect,manager,teacher,andauthor.Naftalin,acertifiedJavaprogrammer,hasworked
ineveryreleaseofJavatodate.HisexperienceinJavaandbusinessgiveshimaunique
perspectiveonthefundamentalchangethatcomeswithintroducinglambdaexpres-
sionsinJavaSE8.Naftalinisafrequentpresenteratconferencesworldwide,includ-
ingtheannualJavaOne.HerunsapopulartutorialsiteincollaborationwithOracle’s
development team, www.lambdafaq.org, focused on the new language features in
Java8.
About the Technical Editors
StuartMarksworksontheJDKCoreLibrariesteamintheJavaPlatformGroupatOra-
cle.Heiscurrentlyworkingonlambda,streams,andcollections,aswellasimproving
testqualityandperformance.HehaspreviouslyworkedonJavaFXandJavaMEatSun
Microsystems.Hehasover20yearsofsoftwareplatformproductdevelopmentexperi-
enceintheareasofwindowsystems,interactivegraphics,andmobileandembedded
systems.Stuartholdsamaster’sdegreeinComputerScienceandabachelor’sdegree
inElectricalEngineeringfromStanfordUniversity.Heliveswithhiswifeanddaughter
inCalifornia.
Brian Goetz is one of the leading authorities on Java programming. He is the author
oftheverysuccessfulJavaConcurrencyinPractice,aswellasover75articlesonJava
development.HewasthespecificationleadforJSR-335(LambdaExpressionsforthe
JavaLanguage)andhasservedonnumerousotherJCPExpertGroups.BrianistheJava
LanguageArchitectatOracle.
Contents
Foreword ...................................................... xi
Acknowledgments ............................................... xiii
Introduction .................................................... xv
1 TakingJavatotheNextLevel .................................... 1
1.1 FromExternaltoInternalIteration............................. 2
1.1.1 InternalIteration .................................... 4
1.1.2 TheCommandPattern................................ 5
1.1.3 LambdaExpressions ................................. 7
1.2 FromCollectionstoStreams ................................. 9
1.3 FromSequentialtoParallel .................................. 12
1.4 ComposingBehaviors ...................................... 15
1.5 Conclusion .............................................. 17
2 TheBasicsofJavaLambdaExpressions............................. 19
2.1 WhatIsaLambdaExpression? ............................... 20
2.1.1 TheSyntaxofLambdas ............................... 20
2.2 Lambdasvs.AnonymousInnerClasses ......................... 21
2.2.1 NoIdentityCrisis.................................... 22
2.2.2 ScopingRulesforLambdas ............................ 22
2.3 VariableCapture.......................................... 23
2.4 FunctionalInterfaces....................................... 26
2.5 UsingLambdaExpressions .................................. 30
2.6 MethodandConstructorReferences ........................... 31
2.6.1 StaticMethodReferences ............................. 32
2.6.2 InstanceMethodReferences ........................... 33
2.6.3 ConstructorReferences ............................... 35
vii
viii MasteringLambdas
2.7 TypeChecking ........................................... 35
2.7.1 WhatExactlyIsaFunctionType? ....................... 36
2.7.2 MatchingaFunctionType............................. 36
2.8 OverloadResolution....................................... 38
2.8.1 OverloadingwithLambdaExpressions ................... 39
2.8.2 OverloadingwithMethodReferences .................... 41
2.9 Conclusion .............................................. 42
3 IntroductiontoStreamsandPipelines ............................. 43
3.1 StreamFundamentals ...................................... 44
3.1.1 Parallel-ReadyCode ................................. 47
3.1.2 PrimitiveStreams.................................... 48
3.2 AnatomyofaPipeline ..................................... 49
3.2.1 StartingPipelines.................................... 50
3.2.2 TransformingPipelines ............................... 51
3.2.3 Non-interference.................................... 60
3.2.4 EndingPipelines .................................... 62
3.3 Conclusion .............................................. 71
4 EndingStreams:CollectionandReduction .......................... 73
4.1 UsingCollectors .......................................... 76
4.1.1 Stand-alonePredefinedCollectors....................... 76
4.1.2 ComposingCollectors ................................ 80
4.1.3 ChainingPipelines .................................. 84
4.1.4 WorkedExample:MostPopularTopics ................... 86
4.2 AnatomyofaCollector..................................... 88
4.2.1 ConcurrentCollection................................ 90
4.3 WritingaCollector ........................................ 90
4.3.1 Finishers .......................................... 94
4.3.2 WorkedExample:FindingMyBooks..................... 97
4.3.3 RulesforCollectors .................................. 101
4.4 Reduction............................................... 102
4.4.1 ReductionoverPrimitives ............................. 102
4.4.2 ReductionoverReferenceStreams ...................... 104
4.4.3 ComposingCollectorswithReduction.................... 108
4.5 Conclusion .............................................. 109
5 StartingStreams:SourcesandSpliterators .......................... 111
5.1 CreatingStreams.......................................... 112
5.2 SpliteratorsandFork/Join ................................... 119
5.2.1 StreamsfromSpliterators.............................. 122
5.3 Exceptions .............................................. 123
Contents ix
5.4 WorkedExample:Recursivegrep ............................. 127
5.5 Conclusion .............................................. 136
6 StreamPerformance ........................................... 137
6.1 Microbenchmarking ....................................... 140
6.1.1 MeasuringaDynamicRuntime ......................... 140
6.1.2 TheJavaMicrobenchmarkingHarness.................... 142
6.1.3 ExperimentalMethod ................................ 143
6.2 ChoosingExecutionMode .................................. 146
6.3 StreamCharacteristics...................................... 148
6.4 Ordering................................................ 151
6.5 StatefulandStatelessOperations ............................. 153
6.6 BoxingandUnboxing...................................... 153
6.7 SpliteratorPerformance..................................... 154
6.8 CollectorPerformance ..................................... 155
6.8.1 ConcurrentMapMerge ............................... 156
6.8.2 PerformanceAnalysis:PointGrouping ................... 157
6.8.3 PerformanceAnalysis:FindingMyBooks ................. 157
6.9 Conclusion .............................................. 158
7 APIEvolutionwithDefaultMethods .............................. 159
7.1 UsingDefaultMethods..................................... 162
7.2 WhatRoleforAbstractClasses? .............................. 164
7.3 DefaultMethodSyntax ..................................... 165
7.4 DefaultMethodsandInheritance ............................. 166
7.4.1 CompatibilityProblems............................... 170
7.5 StaticMethodsinInterfaces ................................. 172
7.5.1 UsingStaticMethods................................. 173
7.6 Conclusion .............................................. 173
Conclusion .................................................. 175
Index ...................................................... 177
