Functional Interfaces in Java (eBook)

Ralph Lecessi is a software engineer with over 30 years’ professional programming experience in the aerospace, telecommunications, and payment industries at companies including Lockheed Martin, Alcatel-Lucent, AT&T, and Northrop Grumman. He is currently lead embedded software developer at TranSendIT, Inc in Mount Laurel, New Jersey.Ralph is also the author of JAVATM - The Beginnings—a text on basic Java programming that includes many examples and diagrams. Ralph is an adjunct professor of programming at Middlesex County College, where he teaches basic and object-oriented programming in Java. He lives in South Brunswick, New Jersey, with his wife and two children.

Table of Contents 4
About the Author 13
About the Technical Reviewer 14
Foreword 15
Chapter 1: Functional Interfaces 16
Section 1.1: Interfaces in Java 16
Section 1.2: Enhancements to Interfaces in Java 8 and Java 9 17
Section 1.3: Functional Interfaces Defined 20
Section 1.4: Implementing Functional Interfaces with Pre-Java 8 Constructs 21
Section 1.5: Providing Default Methods in  Functional Interfaces 23
Section 1.6: Providing Static Methods in Functional Interfaces 26
Section 1.7: Generic Functional Interfaces 28
Section 1.7.1: Generic Functional Interfaces with Type Restrictions 29
Section 1.8: Specializing a Generic Functional Interface 32
PROJECT 1: Playful Pets 35
Problem Statement 35
Solution 35
Short Problems 40
Long Problems 41
Chapter 2: Lambda Expressions 43
Section 2.1: Lambda Expressions Defined 43
Section 2.2: Using Lambda Expressions to  Represent Functional Interfaces 43
Section 2.3: The Scope of a Lambda Expression 45
Section 2.4: Lambda Argument List Variations 46
Section 2.5: Lambda Bodies in Block Form 48
Section 2.6: Limitations of Lambda Expressions 51
PROJECT 2: Compute Square 54
Problem Statement 54
Solution 54
Short Problems 57
Long Problems 57
Chapter 3: Predicates 58
Section 3.1: The java.util.function Package 58
Section 3.2: The Predicate Interface 58
Section 3.3: Passing a Predicate to a Method 60
Section 3.4: Chains of Functional Interfaces 63
Section 3.5: Predicate Chaining Creates Complex Logical Expressions 63
Section 3.5.1: Chains Involving the OR Operation 63
Section 3.5.2: Chains Involving the AND Operation 65
Section 3.5.3: Chains Involving the ! Operation 66
Section 3.5.4: Using Predicate.isEqual 67
Section 3.5.5: Using Predicate.not [JAVA 11] 68
Section 3.6: Overriding Predicate Default Methods 69
Section 3.7: Specializations of Predicates 70
Section 3.8: Binary Predicates 72
PROJECT 3: Discount Dave 72
Problem Statement 72
Solution 73
Short Problems 80
Long Problems 80
Chapter 4: Functions 82
Section 4.1: The Function Interface 82
Section 4.2: Passing a Generic Function to a Method 83
Section 4.2.1: Passing a Function with Restricted or Known Type Parameters 84
Section 4.3: Function Chaining 86
Section 4.3.1: Chains Involving the andThen Method 86
Section 4.3.2: Chains Involving the compose Method 86
Section 4.4: The Function.identity Method 87
Section 4.5: Specializations of Functions Which Convert from Primitive Types 88
Section 4.6: Specializations of Functions Which Convert to Primitive Types 89
Section 4.7: Non-generic Specializations of Functions 90
Section 4.8: Binary Functions 90
Section 4.9: Creating Chains Using BiFunctions 91
Section 4.10: Specializations of BiFunctions Which Convert to Primitive Types 92
PROJECT 4: Sales Promotions 93
Problem Statement 93
Solution 93
Short Problems 105
Long Problems 106
Chapter 5: Operators 107
Section 5.1: The UnaryOperator Interface 107
Section 5.2: Specializations of UnaryOperator 108
Section 5.2.1: Chains Involving UnaryOperator Specializations 109
Section 5.3: The BinaryOperator Interface 110
Section 5.4: Non-generic Specializations of  BinaryOperator 111
PROJECT 5: Calculator 112
Problem Statement 112
Solution 112
Short Problems 118
Long Problems 119
Chapter 6: Consumers 120
Section 6.1: The Consumer Interface 120
Section 6.2: Using Chains of Consumers to Compute Equations 121
Section 6.3: Using Consumers with println as the Terminal Operation 123
Section 6.4: Non-generic Specializations of Consumers 123
Section 6.5: The BiConsumer Interface 125
Section 6.6: Specializations of BiConsumer 126
PROJECT 6: Bank Transactions 127
Problem Statement 127
Solution 128
Short Problems 139
Long Problems 140
Chapter 7: Suppliers 141
Section 7.1: The Supplier Interface 141
Section 7.2: Wrapping User Prompts in a Supplier 143
Section 7.3: Non-generic Specializations of Suppliers 145
PROJECT 7: Ticketing System 146
Problem Statement 146
Solution 147
Short Problems 158
Long Problems 159
Chapter 8: Use in Traversing Objects 161
Section 8.1: Traversing Objects Using Iterators 161
Section 8.2: Traversing Java Arrays of Primitive Types 162
Section 8.2.1: Using Specializations of PrimitiveIterator 166
Section 8.3: Traversing Objects Using Spliterators 170
Section 8.4: Traversing Iterable Objects 174
Section 8.5: Traversing Iterable Objects That Contain Java Arrays of Primitives 175
Section 8.5.1: Using Specializations of PrimitiveIterator 179
Section 8.6: Traversing Maps 181
Section 8.7: Traversing Sets 182
PROJECT 8: Payroll 182
Problem Statement 182
Solution 183
Short Problems 189
Long Problems 190
Chapter 9: Use in Collections 191
Section 9.1: Removing Elements from a Collection 191
Section 9.2: Populating an Array 192
Section 9.3: Replacing the Elements of a List or a Map 194
Section 9.4: Parallel Computations on Arrays 195
Section 9.5: Map Computations 196
Section 9.6: Map Merging 199
Section 9.7: Functional Interfaces and Sets 201
PROJECT 9: Department of Motor Vehicles 201
Problem Statement 201
Solution 202
Short Problems 214
Long Problems 216
Chapter 10: Use in Comparing Objects 218
Section 10.1: The Comparator Interface 218
Section 10.2: Some Useful Comparator Methods 220
Section 10.3: The Comparator comparing Methods 221
Section 10.4: Specializations of the Comparator comparing Method 226
Section 10.5: Building Chains of Comparators 227
Section 10.6: Specializing Comparator Chain Components 230
Section 10.7: Using Comparators to Sort Lists 231
Section 10.8: Using Comparators to Sort Java Arrays 233
Section 10.9: Using Comparators to Organize Maps 236
Section 10.10: Using Comparators in BinaryOperator Methods 237
PROJECT 10: Real Estate Broker 238
Problem Statement 238
Solution 239
Short Problems 248
Long Problems 249
Chapter 11: Use in Optionals 252
Section 11.1: Creating an Optional 252
Section 11.2: Determining If an Optional Is Present 253
Section 11.3: Retrieving the Contents of an Optional 254
Section 11.4: Creating Chains of Optionals 255
Section 11.5: Printing the Contents of an Optional 257
Section 11.6: Filtering Optionals 258
Section 11.7: Optional Chains Involving map and flatmap 259
PROJECT 11: Guess a Number 262
Problem Statement 262
Solution 262
Short Problems 265
Long Problems 266
Chapter 12: Use in Streams 267
Section 12.1: Generating Stream Elements 267
Section 12.2: Traversing Streams 268
Section 12.3: Filtering Stream Elements 269
Section 12.4: Converting an Object to a Stream 270
Section 12.5: Sorting Stream Elements 270
Section 12.6: Selecting the Smallest or Largest Element in a Stream 271
Section 12.7: flatMap vs. map 272
Section 12.8: Reducing Stream Elements 274
Section 12.9: Collecting Stream Elements into a Mutable Reduction 275
Section 12.9.1: Using Prewritten Collectors 279
Section 12.10: Building Streams Interactively 284
Section 12.11: Displaying Intermediate Results 285
Section 12.12: Stream Specializations 286
PROJECT 12: Dave’s Part Inventory 287
Problem Statement 287
Solution 287
Short Problems 298
Long Problems 298
Chapter 13: Use in Multithreaded Programs 300
Section 13.1: Performing Computations Using Runnable and Callable 300
Section 13.1.1: Using Runnable in Optionals 304
Section 13.2: Futures and FutureTasks 304
Section 13.3: CompletionStages and  CompletableFutures 305
Section 13.4: Creating CompletableFutures and Retrieving Their Results 306
Section 13.5: Using the thenApply and thenAccept Methods 308
Section 13.6: Processing the First Asynchronous Future to Complete 309
Section 13.7: Making a Future Dependent on Another Future 310
Section 13.8: Cancelling a Future 311
Section 13.9: When Futures Throw Unchecked Exceptions 313
Section 13.10: Running Futures in Parallel 314
PROJECT 13: Sentence Builder 320
Problem Statement 320
Solution 320
Short Problems 333
Long Problems 334
Chapter 14: Use in Atomic Calculations 335
Section 14.1: Atomic Integers 336
Section 14.1.1: Accumulating an Atomic Value 338
Section 14.1.2: Updating an Atomic Value 339
Section 14.1.3: Comparing an Atomic Value 340
Section 14.2: Atomic Longs 343
Section 14.3: Atomic Booleans 344
Section 14.4: Atomic Arrays 344
Section 14.5: Atomic References 345
PROJECT 14: Bank Account 347
Problem Statement 347
Solution 347
Short Problems 351
Long Problems 352
Chapter 15: Use in JavaFX Applications 353
Section 15.1: Handling JavaFX Events 353
Section 15.2: Building JavaFX UI Components 355
Section 15.3: JavaFX Builder Factories 358
Section 15.4: Monitoring Changes in Collections 362
Section 15.4.1: Monitoring List Changes 362
Section 15.4.2: Monitoring Set Changes 368
Section 15.4.3: Monitoring Map Changes 372
Section 15.5: Invalidating an Observable Object 376
PROJECT 15: DMV GUI 380
Problem Statement 380
Solution 380
Short Problems 394
Long Problems 395
Appendix: Method References 397
Section A.1: Using References to Static Methods to Represent Functional Interfaces 397
Section A.2: References to Instance Methods 399
Section A.3: References to Constructors 400
Section A.4: Passing Method References as Arguments 401
Section A.5: Representing Functions with Method References 403
Section A.6: Using Method References with Comparators 405
Section A.7: Using Method References with Streams 406
Index 410