Java Programming Exercises Volume Two Java Standard Library (Christian Ullenboom) (Z-Library)

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Java Programming Exercises Take the next step in raising your coding skills and dive into the intricacies of Java Standard Libraries. You will continue to raise your coding skills, and test your Java knowledge on tricky programming tasks, with the help of the pirate Captain CiaoCiao. This is the second of two volumes which provide you with everything you need to excel in your Java journey, including tricks that you should know in detail as a professional, as well as intensive training for clean code and thoughtful design that carries even complex software. Features: • 149 tasks with commented solutions on different levels • For all paradigms: object‑oriented, imperative, and functional • Clean code, reading foreign code, and object‑oriented modeling With numerous best practices and extensively commented solutions to the tasks, these books provide the perfect workout for professional software development with Java.

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Java Programming Exercises Volume Two: Java Standard Library Christian Ullenboom

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Designed cover image: Mai Loan Nguyen Duy, Rheinwerk Verlag GmbH First edition published 2025 by CRC Press 2385 NW Executive Center Drive, Suite 320, Boca Raton FL 33431 and by CRC Press 4 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN CRC Press is an imprint of Taylor & Francis Group, LLC ©2023 Christian Ullenboom. First published in the German language under the title “Captain CiaoCiao erobert Java” (ISBN 978‑3‑8362‑8427‑1) by Rheinwerk Verlag GmbH, Bonn, Germany. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, access www.copyright.com or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978‑750‑8400. For works that are not available on CCC please contact mpkbookspermissions@tandf.co.uk Trademark notice: Product or corporate names may be trademarks or registered trademarks and are used only for identification and explanation without intent to infringe. ISBN: 978‑1‑032‑80117‑9 (hbk) ISBN: 978‑1‑032‑79801‑1 (pbk) ISBN: 978‑1‑003‑49555‑0 (ebk) DOI: 10.1201/9781003495550 Typeset in Times by codeMantra Access the Support Material: https://routledge.com/9781032798011

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v Contents About the Author xiii Introduction 1 Previous Knowledge and Target Audience 1 Working with the Book 2 The Suggested Solutions 2 Use of the Book 3 Required Software 3 Used Java Version in the Book 4 JVM 4 Development Environment 4 Conventions 4 Helping Captain CiaoCiao and Bonny Brain 5 1 Advanced String Processing 6 Format Strings 6 Build ASCII Table ⭑ 6 Aligned Outputs ⭑ 8 Regular Expressions and Pattern Recognition 8 Quiz: Define Regex ⭑ 8 Determine Popularity in Social Media ⭑ 8 Detect Scanned Values ⭑ 9 Quiet Please! Defuse Shouting Texts ⭑ 10 Converting Time from AM/PM Format to 24‑Hour Format ⭑⭑ 11 Decompose Strings into Tokens 12 Split Address Lines with the StringTokenizer ⭑ 12 Split Sentences into Words and Reverse Them ⭑ 13 Check Relations between Numbers ⭑ 13 Convert A1 Notation to Columns and Rows ⭑⭑ 13 Parse Simple CSV Files with Coordinates ⭑ 14 Compress Strings Lossless by Runlength Encoding ⭑⭑⭑ 14 Character Encodings and Unicode Collation Algorithm 15 Quiz: Encoding for Unicode Characters ⭑ 15 Quiz: Order of Strings with and without Collator ⭑ 16 Suggested Solutions 16 Build ASCII Table 16 Aligned Outputs 17 Quiz: Define Regex 18 Determine Popularity in Social Media 19 Detect Scanned Values 19 Quiet Please! Defuse Shouting Texts 20 Converting Time from AM/PM Format to 24‑Hour Format 20 Split Address Lines with the StringTokenizer 21

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vi Contents Split Sentences into Words and Reverse Them 22 Check Relations between Numbers 23 Convert A1 Notation to Columns and Rows 24 Parse Simple CSV Files with Coordinates 25 Compress Strings Lossless by Runlength Encoding 26 Quiz: Encoding for Unicode Characters 28 Quiz: Order of Strings with and without Collator 28 2 Mathematics 30 The Class Math 30 Quiz: Rule of Thumb ⭑ 30 Check If Tin Tin Cheated on Rounding ⭑ 31 Huge and Very Precise Numbers 32 Calculate Arithmetic Mean of a Large Integer ⭑ 32 Number by Number over the Phone ⭑ 33 Develop Class for Fractions and Truncate Fractions ⭑⭑ 34 Suggested Solutions 35 Quiz: Rule of Thumb 35 Check If Tin Tin Cheated on Rounding 36 Calculate Arithmetic Mean of a Large Integer 37 Number by Number over the Phone 38 Develop Class for Fractions and Truncate Fractions 38 3 Locale, Date, and Time 42 Languages and Countries 42 Apply Country‑/Language‑Specific Formatting for Random Number ⭑ 43 Date and Time Classes 44 Formatting Date Output in Different Languages ⭑ 44 On Which Day Does Sir Francis Beaufort Celebrate His Birthday? ⭑ 45 Find All Friday the 13th ⭑ 45 Get Average Duration of Karaoke Nights ⭑ 46 Parse Different Date Formats ⭑⭑⭑ 46 Suggested Solutions 47 Apply Country‑/Language‑Specific Formatting for Random Number 47 Formatting Date Output in Different Languages 47 On Which Day Does Sir Francis Beaufort Celebrate His Birthday? 48 Find All Friday the 13th 50 Get Average Duration of Karaoke Nights 51 Parse Different Date Formats 52 4 Concurrent Programming with Threads 54 Create Threads 55 Create Threads for Waving and Flag Waving ⭑ 56 No More Waving Flags: End Threads ⭑ 56 Parameterize Runnable ⭑⭑ 56 Execute and Idle 57 Delay Execution by Sleeping Threads ⭑⭑ 57 Watch File Changes by Threads ⭑ 58 Catch Exceptions ⭑ 58 Thread Pools and Results 59 Using Thread Pools ⭑⭑ 60 Get Last Modification of Web Pages ⭑⭑ 60

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Contents vii Protect Critical Sections 61 Writing Memories into a Poetry Album ⭑ 62 Thread Cooperation and Synchronization Helper 64 Attending the Banquet with the Captains—Semaphore ⭑⭑ 64 Swearing and Insulting—Condition ⭑⭑ 65 Take Pens Out of Paintbox—Condition ⭑⭑ 65 Play Rock, Paper, Scissors—CyclicBarrier ⭑⭑⭑ 66 Find the Fastest Runner—CountDownLatch ⭑⭑ 67 Suggested Solutions 68 Create Threads for Waving and Flag Waving 68 No More Waving Flags: End Threads 69 Parameterize Runnable 70 Delay Execution by Sleeping Threads 70 Watch File Changes by Threads 72 Catch Exceptions 73 Using Thread Pools 74 Get Last Modification of Web Pages 75 Writing Memories into a Poetry Album 77 Attending the Banquet with the Captains—Semaphore 78 Swearing and Insulting—Condition 79 Take Pens Out of Paintbox—Condition 80 Play Rock, Paper, Scissors—CyclicBarrier 82 Find the Fastest Runner—CountDownLatch 83 5 Data Structures and Algorithms 85 The Types of the Collection API 86 Quiz: Search for StringBuilder ⭑ 87 Lists 88 Singing and Cooking: Traverse Lists and Check Properties ⭑ 88 Filter Comments from Lists ⭑ 89 Shorten Lists Because There Is No Downturn ⭑ 89 Eating with Friends: Compare Elements, Find Commonalities ⭑ 90 Check Lists for the Same Order of Elements ⭑ 90 And Now the Weather: Find Repeated Elements ⭑ 91 Generate Receipt Output ⭑ 92 Quiz: Arrays Decorated ⭑ 92 Quiz: Searched and Not Found ⭑ 92 Everything Tastes Better with Cheese: Insert Elements into Lists ⭑ 93 Quiz: With Nothing but Trouble ⭑ 93 Search Elements with the Iterator and Find Covid Cough ⭑⭑ 94 Move Elements, Play Musical Chairs ⭑ 95 Programming a Question Game with Planets ⭑⭑ 95 Sets 97 Form Subsets, Find Common Elements ⭑ 97 Quiz: Great Swords ⭑ 98 Get All Words Contained in a Word ⭑⭑ 99 Exclude Duplicate Elements with a UniqueIterator ⭑⭑ 99 Map Keys to Values 100 Convert Two‑Dimensional Arrays to Map ⭑ 100 Convert Text to Morse Code and Vice Versa ⭑ 101 Remember Word Frequency with Associative Memory ⭑⭑ 101 Read In and Read Out Colors ⭑⭑ 102

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viii Contents Read in Names and Manage Lengths ⭑ 103 Find Missing Characters ⭑⭑ 103 Calculate Number of Paths to the Three‑Headed Monkey ⭑⭑ 103 Manage Holidays in a Sorted Associative Store ⭑ 104 Quiz: Keys in a HashMap ⭑⭑ 105 Determine Commonality: Party Set and Souvenir ⭑ 106 Properties 106 Develop Convenient Properties Decorator ⭑⭑ 106 Stack and Queues 108 Program RPN Pocket Calculator ⭑ 108 BitSet 109 Forget No Ship ⭑ 109 Find Duplicate Entries and Solve the Animal Chaos ⭑ 110 Thread‑Safe Data Structures 110 Loading Ship ⭑⭑ 111 Handle Important Messages First ⭑⭑ 112 If Used Up, Create a New One ⭑⭑⭑ 113 Suggested Solutions 114 Quiz: Search for StringBuilder 114 Singing and Cooking: Traverse Lists and Check Properties 114 Filter Comments from Lists 116 Shorten Lists Because There Is No Downturn 117 Eating with Friends: Compare Elements, Find Commonalities 118 Check Lists for the Same Order of Elements 118 And Now the Weather: Find Repeated Elements 120 Generate Receipt Output 121 Quiz: Arrays Decorated 123 Quiz: Searched and Not Found 124 Everything Tastes Better with Cheese: Insert Elements into Lists 124 Quiz: With Nothing but Trouble 125 Search Elements with the Iterator and Find Covid Cough 126 Move Elements, Play Musical Chairs 128 Programming a Question Game with Planets 129 Form Subsets, Find Common Elements 130 Quiz: Great Swords 131 Get All Words Contained in a Word 132 Exclude Duplicate Elements with a UniqueIterator 133 Convert Two‑Dimensional Arrays to Map 134 Convert Text to Morse Code and Vice Versa 136 Remember Word Frequency with Associative Memory 138 Read In and Read Out Colors 140 Read in Names and Manage Lengths 141 Find Missing Characters 143 Calculate the Number of Paths to the Three‑Headed Monkey 145 Manage Holidays in a Sorted Associative Store 146 Quiz: Keys in a HashMap 147 Determine Commonality: Party Set and Souvenir 148 Develop Convenient Properties Decorator 148 Program RPN Pocket Calculator 150 Forget No Ship 151 Find Duplicate Entries and Solve the Animal Chaos 152 Loading Ship 153

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Contents ix Handle Important Messages First 154 If Used Up, Create a New One 155 Notes 156 6 Java Stream-API 157 Regular Streams with Their Terminal and Intermediate Operations 157 Hero Epic: Meet Stream API ⭑ 157 Quiz: Double Output ⭑ 158 Get the Beloved Captain from a List ⭑ 158 Frame Pictures ⭑ 159 Look and Say ⭑⭑ 160 Remove Duplicate Islands of Rare Earth Metals ⭑⭑⭑ 161 Where Are the Sails? ⭑⭑ 162 Buy the Most Popular Car ⭑⭑⭑ 163 Primitive Streams 163 Detect NaN in an Array ⭑ 163 Generate Decades ⭑ 164 Generate Array with Constant Content via Stream ⭑ 164 Draw Pyramids ⭑ 165 Teddies Labeled with Letters ⭑ 165 Get the Letter Frequency of a String ⭑ 166 From 1 to 0, from 10 to 9 ⭑⭑ 166 The Annual Octopus Contest ⭑⭑ 166 Merge Three int Arrays ⭑ 167 Determine Winning Combinations ⭑⭑ 167 Statistics 168 The Fastest and Slowest Paddlers ⭑ 168 Calculate Median ⭑⭑ 169 Calculate Temperature Statistics and Draw Charts ⭑⭑⭑ 169 Suggested Solutions 170 Hero Epic: Meet Stream API 170 Quiz: Double Output 176 Get the Beloved Captain from a List 176 Frame Pictures 177 Look and Say 178 Remove Duplicate Islands of Rare Earth Metals 179 Where Are the Sails? 181 Buy the Most Popular Car 182 Detect NaN in an Array 183 Generate Decades 183 Generate Array with Constant Content via Stream 184 Teddies Labeled with Letters 184 Draw Pyramids 185 Get the Letter Frequency of a String 185 From 1 to 0, from 10 to 9 186 The Annual Octopus Contest 187 Merge Three int Arrays 188 Determine Winning Combinations 189 The Fastest and Slowest Paddlers 189 Calculate Median 190 Calculate Temperature Statistics and Draw Charts 191 Note 195

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x Contents 7 Files, Directories, and File Access 196 Path and Files 196 Display Saying of the Day ⭑ 197 Merge Hiding Places ⭑ 197 Create Copies of a File ⭑⭑ 197 Generate a Directory Listing ⭑ 198 Search for Large GIF Files ⭑ 198 Descend Directories Recursively and Find Empty Text Files ⭑ 198 Develop Your Own Utility Library for File Filters ⭑⭑⭑ 199 Random Access to File Contents 199 Output Last Line of a Text File ⭑⭑ 200 Suggested Solutions 200 Display Saying of the Day 200 Merge Hiding Places 201 Create Copies of a File 201 Generate a Directory Listing 202 Search for Large GIF Files 203 Descend Directories Recursively and Find Empty Text Files 204 Develop Your Own Utility Library for File Filters 205 Output Last Line of a Text File 208 8 Input/Output Streams 210 Direct Data Streams 211 Get the Number of Different Places (Read Files) ⭑ 211 Convert Python Program to Java (Write File) ⭑ 211 Generate Target Code (Write File) ⭑ 212 Convert File Contents to Lowercase (Read and Write File) ⭑ 213 Convert PPM Graphics to ASCII Grayscale ⭑⭑⭑ 213 Split Files (Read and Write Files) ⭑⭑ 215 Nesting Streams 215 Quiz: DataInputStream and DataOutputStream ⭑ 215 Compress Number Sequences with the GZIPOutputStream ⭑ 216 Serialization 216 (De)serialize Data for Chat and Convert It to Text ⭑⭑ 216 Quiz: Requirement for Serialization ⭑ 217 Save Last Inputs ⭑⭑ 217 Suggested Solutions 218 Get the Number of Different Places (Read Files) 218 Convert Python Program to Java (Write File) 219 Generate Target Code (Write File) 220 Convert File Contents to Lowercase (Read and Write File) 221 Convert PPM Graphics to ASCII Gray Scale 222 Split Files (Read and Write Files) 224 Quiz: DataInputStream and DataOutputStream 225 Compress Number Sequences with the GZIPOutputStream 228 (De)serialize Data for Chat and Convert Them to Text 229 Quiz: Requirement for Serialization 230 Save Last Inputs 231 Note 233

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Contents xi 9 Network Programming 234 URL and URLConnection 234 Download Remote Images via URL ⭑ 235 Read Remote Text File from URL ⭑ 235 HTTP Client 236 Top News from Hacker News ⭑⭑ 236 Socket and ServerSocket 237 Implement a Swear Server and a Client ⭑⭑ 237 Implement a Port Scanner ⭑⭑ 237 Suggested Solutions 238 Download Remote Images via URL 238 Read Remote Text File from URL 239 Top News from Hacker News 240 Implement a Swear Server and a Client 241 Implement a Port Scanner 243 10 Process XML, JSON, and Other Data Formats 246 XML Processing with Java 247 Write XML File with Recipe ⭑ 247 Check If All Images Have an alt Attribute ⭑ 248 Writing Java Objects with JAXB ⭑ 248 Read in Jokes and Laugh Heartily ⭑⭑ 249 JSON 251 Hacker News JSON Exploit ⭑ 251 Read and Write Editor Configurations as JSON ⭑⭑ 252 HTML 253 Load Wikipedia Images with jsoup ⭑⭑ 253 Office Documents 253 Generate Word Files with Screenshots ⭑⭑ 253 Archives 254 Play Insect Sounds from ZIP Archive ⭑⭑ 254 Suggested Solutions 255 Write XML File with Recipe 255 Check If All Images Have an alt Attribute 258 Writing Java Objects with JAXB 259 Read in Jokes and Laugh Heartily 260 Hacker News JSON Exploit 261 Read and Write Editor Configurations as JSON 262 Load Wikipedia Images with jsoup 263 Generate Word Files with Screenshots 264 Play Insect Sounds from ZIP Archive 265 Note 266 11 Database Access with JDBC 267 Database Management Systems 267 Prepare H2 Database ⭑ 268 Database Queries 268 Query All Registered JDBC Drivers ⭑ 268 Build Database and Execute SQL Script ⭑ 269 Insert Data into the Database ⭑ 270 Insert Data into the Database in Batch Mode ⭑ 271

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xii Contents Insert Data with Prepared Statements ⭑ 271 Request Data ⭑ 272 Interactive Scrolling through the ResultSet ⭑ 272 Pirate Repository ⭑⭑ 272 Query Column Metadata ⭑ 273 Suggested Solutions 274 Query All Registered JDBC Drivers 274 Build Database and Execute SQL Script 274 Insert Data into the Database 275 Insert Data into the Database in Batch Mode 276 Insert Data with Prepared Statements 277 Request Data 277 Interactive Scrolling through the ResultSet 278 Pirate Repository 279 Query Column Metadata 282 12 Operating System Access 284 Console 284 Colored Console Outputs ⭑ 285 Properties 286 Windows, Unix, or macOS? ⭑ 286 Unify Command‑Line Properties and Properties from Files ⭑ 286 Execute External Processes 287 Read the Battery Status via Windows Management Instrumentation ⭑⭑ 287 Suggested Solutions 288 Colored Console Outputs 288 Windows, Unix, or macOS? 288 Unify Command‑Line Properties and Properties from Files 289 Read the Battery Status via Windows Management Instrumentation 290 13 Reflection, Annotations, and JavaBeans 294 Reflection API 294 Create UML Class Diagram with Inheritance Relationships ⭑ 295 Create UML Class Diagram with Properties ⭑ 296 Generate CSV Files from List Entries ⭑⭑ 297 Annotations 297 Create CSV Documents from Annotated Instance Variables ⭑⭑ 297 Suggested Solutions 298 Create UML Class Diagram with Inheritance Relationships 298 Create UML Class Diagram with Properties 299 Generate CSV Files from List Entries 301 Create CSV Documents from Annotated Instance Variables 301 Epilogue 307 Code Golf Stack Exchange 307 Project Euler 307 Daily Programmer 307 Rosetta Code 308

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xiii About the Author Christian Ullenboom started his programming journey at the tender age of ten, typing his first lines of code into a C64. After mastering assembler programming and early BASIC extensions, he found his call‑ ing on the island of Java, following his studies in computer science and psychology. Despite indulging in Python, JavaScript, TypeScript, and Kotlin vacations, he remains a savant of all things Java. For over 20 years, Ullenboom has been a passionate software architect, Java trainer (check out http:// www.tutego.com), and IT specialist instructor. His expertise has resulted in a number of online video courses and reference books: • Java: The Comprehensive Guide (ISBN‑13: 978‑1493222957) • Java ist auch eine Insel: Java programmieren lernen mit dem umfassenden Standardwerk für Java‑Entwickler (ISBN‑13: 978‑3836287456) • Java SE 9 Standard‑Bibliothek: Das Handbuch für Java‑Entwickler (ISBN‑13: 978‑3836258746) • Captain CiaoCiao erobert Java: Das Trainingsbuch für besseres Java (ISBN‑13: 978‑3836284271) • Spring Boot 3 und Spring Framework 6: Professionelle Enterprise‑Anwendungen mit Java ( ISBN‑13: 978‑3836290494) Christian Ullenboom has been spreading Java love through his books for years, earning him the coveted title of Java Champion from Sun (now Oracle) way back in 2005. Only a select few—about 300 world‑ wide—have achieved this status, making him a true Java superstar. As an instructor, Ullenboom understands that learning by doing is the most effective way to master a skill. So, he has compiled a comprehensive catalog of exercises that accompany his training courses. This book features a selection of those exercises, complete with documented solutions. His roots are in Sonsbeck, a small town in the Lower Rhine region of Germany.

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DOI: 10.1201/9781003495550‑1 1 Introduction Many beginners in programming often ask themselves, “How can I strengthen my skills as a developer? How can I become a better programmer?” The answer is simple: study, attend webinars, learn, repeat, practice, and discuss your work with others. Many aspects of programming are similar to learning new skills. Just as a book can’t teach you how to play a musical instrument, watching the Fast and the Furious movie series won’t teach you how to drive. The brain develops patterns and structures through repeated practice. Learning a programming language and a natural language have many similarities. Consistent use of the language, and the desire and need to express and communicate in it (just as you need to do so to order a burger or a beer), leads to gradual improvement in skills. Books and webinars on learning a programming language are available, but reading, learning, prac‑ ticing, and repeating are just one aspect of becoming a successful software developer. To create effective software solutions, you need to creatively combine your knowledge, just as a musician regularly practices finger exercises and maintains their repertoire. The more effective your exercises are, the faster you will become a master. This book aims to help you progress and gain more hands‑on experience. Java 21 declares more than 2300 classes, about 1400 interfaces, around 140 enumerations, approxi‑ mately 500 exceptions, and a few annotation types and records are added to this. However, in practical terms, only a small subset of these types proves to be relevant. This book selects the most important types and methods for tasks, making them motivating, and following Java conventions. Alternative solutions and approaches are also presented repeatedly. The goal is to make non‑functional requirements clear because the quality of programs is not just about “doing what it should.” Issues such as correct indentation, following naming conventions, proper use of modifiers, best practices, and design patterns are essential. The proposed solutions aim to demonstrate these principles, with the keyword being Clean Code. PREVIOUS KNOWLEDGE AND TARGET AUDIENCE The book is aimed at Java developers who are either new to Java or are already advanced and wish to learn more about the Java SE standard libraries. The intended audience includes: • Computer science students • IT specialists • Java programmers • Software developers • Job applicants The book is centered around tasks and fully documented solutions, with detailed explanations of Java peculiarities, good object‑oriented programming practices, best practices, and design patterns. The exer‑ cises are best solved with a textbook, as this exercise book is not a traditional textbook. A useful approach is to work through a topic with a preferred textbook before attempting the exercises that correspond to it.

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2 Java Programming Exercises The first set of tasks are designed for programming beginners who are new to Java. As you gain more experience with Java, the tasks become more challenging. Therefore, there are tasks for both beginners and advanced developers. The Java Standard Edition is augmented by numerous frameworks and libraries. However, this exercise book does not cover specific libraries or Java Enterprise frameworks like Jakarta EE or Spring (Boot). There are separate exercise books available for these environments. Additionally, the book does not require the use of tools like profiling tools, as these are beyond the scope of the book. WORKING WITH THE BOOK The task book is organized into different sections. The first section covers the Java language, followed by selected areas of the Java standard library, such as data structures or file processing. Each area is accompanied by programming tasks and “quiz” questions that contain surprises. Each section starts with a small motivation and characterization of the topic, followed by the exercises. Additional tips and hints are provided for particularly challenging assignments, while other exercises offer optional extensions for further exploration. The majority of exercises are independent of each other, making it easy for readers to dive in any‑ where. However, in the chapter on imperative programming, some tasks build on each other to develop a larger program, and the same goes for the chapter on object‑oriented programming. The problem defini‑ tions make this clear, and more complex programs help to provide context for understanding different language characteristics. Furthermore, a more complex program can motivate readers to continue. The exercises are rated with one, two, or three stars to indicate their complexity, although this rating is subjective to the author. 1 star ★: Simple exercises, suitable for beginners. They should be easy to solve without much effort. Often only transfer of knowledge is required, for example, by writing down things that are in a textbook differently. 2 stars ★★: The effort is higher here. Different techniques have to be combined. Greater creativity is required. 3 stars ★★★: Assignments with three stars are more complex, require recourse to more prior knowledge, and sometimes require research. Frequently, the tasks can no longer be solved with a single method, but require multiple classes that must work together. THE SUGGESTED SOLUTIONS The task book provides at least one suggested solution for each problem. The term “sample solution” is not used to avoid implying that the given solution is the best one and that all other solutions are useless. Readers are encouraged to compare their solutions with the proposed solution and can be satisfied if their solution is more elegant. All proposed solutions are commented, making it possible to follow all steps well. The suggested solutions are compiled at the end of each chapter to reduce the temptation to look into a solution directly after the task, which takes the fun out of solving the task. The suggested solutions can also be found on the website https://github.com/ullenboom/captain‑ciaociao. Some solutions contain com‑ ments of the type //tag::solution[], which marks the parts of the solutions printed in the book.

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• Introduction 3 USE OF THE BOOK To become a software developer, you must master the art of turning problems into code, and that’s where practice and role models come in. While there are plenty of exercises available online, they’re often disorganized, poorly documented, and outdated. That’s where this book shines, by offering a systematic approach to tasks and well‑thought‑out solutions. Studying these solutions and reading code in general helps the brain develop patterns and solutions that can be applied to future coding challenges. It’s like reading the Bible; you need to read to understand and learn. Surprisingly, many software developers write code without bothering to read others’ code, which can lead to confusion and misunderstand‑ ing. Reading good code elevates our writing skills by building patterns and solutions that our brains unconsciously transfer to our own code. Our brains form neuronal structures independently based on templates, and the quality of the input we receive matters greatly. Therefore, we should only feed our brains with good code, as bad solutions make for bad models. The book covers important topics such as exception handling or error handling, discussing the correct input values, identifying erroneous states, and how to handle them. In software, things can and will go wrong, and we must be prepared to deal with the less‑than‑perfect world. It’s easy for developers to get stuck in their ways of writing code, which is why it’s important to explore new approaches and “expand our vocabulary”, so to speak. For Java developers, libraries are their vocabulary, but too many enterprise Java developers write massive, non‑object‑oriented code. The solu‑ tion is to continuously improve object‑oriented modeling, which is precisely what this book demonstrates. It introduces new methods, creates new data types, and minimizes complexity. Additionally, functional programming is becoming increasingly important in Java development, and all solutions in this book take advantage of modern language features. While some solutions may appear overly complex, the tasks and proposed solutions in this book can help developers improve their ability to concentrate and follow through with steps. In practice, the ability to concentrate and quickly comprehend code is crucial for developers. Often, developers must join a new team and be able to understand and modify unfamiliar source code, and possibly fix bugs. Those who wish to expand upon existing open‑source solutions can also benefit from honing their concentration skills through these exercises. In addition to its emphasis on the Java programming language, syntax, libraries, and object orien‑ tation, this book provides numerous side notes on topics such as algorithms, the historical evolution of programming, comparisons to other programming languages, and data formats. These additional insights and perspectives offer readers a more well‑rounded understanding of software development beyond just the technical aspects. If you’re looking for one more reason to add this book to your collection, it doubles as a fantastic sleep aid! REQUIRED SOFTWARE While solving a task with just a pen and paper is possible in theory, modern software development requires the proper use of tools. Knowing programming language syntax, object‑oriented modeling, and libraries is just the tip of the iceberg. Understanding the JVM, using tools like Maven and Git for version management, and becoming proficient in an IDE are all crucial aspects of professional software development. Some developers can even perform magic in their IDE, generating code and fixing bugs automatically.

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4 Java Programming Exercises USED JAVA VERSION IN THE BOOK While Java 8 remains prevalent in enterprise settings, it’s crucial for learners to become acquainted with the latest language features. Accordingly, whenever feasible, the suggested solutions in this book leverage Java 17. Not only is this version equipped with Long‑term Support (LTS), but runtime environment pro‑ viders also offer extensive support, ensuring that the release retains its relevance for an extended period. JVM If we want to run Java programs, we need a JVM. In the early days, this was easy. The runtime environ‑ ment first came from Sun Microsystems, later from Oracle, which took over Sun. Today, it is much more confusing. Although a runtime environment can still be obtained from Oracle, the licensing terms have changed, at least for Java 8 up to Java 16. Testing and development are possible with the Oracle JDK, but not in production. In this case, Oracle charges license fees. As a consequence, various institutions compile their own runtime environments from the OpenJDK, the original sources. The best known are Eclipse Adoptium (https://adoptium.net/), Amazon Corretto (https://aws.amazon.com/de/corretto), Red Hat OpenJDK (https://developers.redhat.com/products/openjdk/overview) and others such as those from Azul Systems or Bellsoft. There is no specific distribution that readers are required to follow. Development Environment Java source code is just plain text, so technically a simple text editor is all you need. However, relying solely on Notepad or vi for productivity is like trying to win a race on a tricycle. Modern integrated development environments support us with many tasks: color highlighting of keywords, automatic code completion, intelligent error correction, insertion of code blocks, visualization of states in the debug‑ ger, and much more. It is therefore advisable to use a full development environment. Four popular IDEs are: IntelliJ, Eclipse, Visual Studio Code, and (Apache) NetBeans. Just like with Java runtime environ‑ ments, the choice of IDE is left to the reader. Eclipse, NetBeans, and Visual Studio Code are all free and open‑source, while IntelliJ Community Edition is also free, but the more advanced IntelliJ Ultimate Edition will cost you some cash. Halfway through the book, we delve into implementing project dependencies using Maven in a few places. CONVENTIONS Code is written in fix width font, filenames are italicized. To distinguish methods from attributes, methods always have a pair of parentheses, such as in “the variable max contains the maximum” or “it returns max() the maximum”. Since methods can be overloaded, either the parameter list is named, as in equals(Object), or an ellipsis abbreviates it, such as in “various println(…) methods”. If a group of identifiers is addressed, * is written, like print*(...) prints something on the screen. In the suggested solutions, there are usually only the relevant code snippets, so as not to blow up the book volume. The name of the file is mentioned in the listing caption, like this: VanillaJava.java class VanillaJava { }

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• Introduction 5 Sometimes, we need to flex our terminal muscles and execute programs from the command line (also known as console or shell). Since each command‑line program has its own prompt sequence, it is symbol‑ ized here in the book with a $. The user’s input is set in bold. Example: $ java ‑version java version "17.0.5" 2022‑10‑18 LTS Java(TM) SE Runtime Environment (build 17.0.5+9‑LTS‑191) Java HotSpot(TM) 64‑Bit Server VM (build 17.0.5+9‑LTS‑191, mixed mode, sharing) If the Windows command line is explicitly meant, the prompt character > is set: > netstat ‑e Interface Statistics Received Sent Bytes 218927776 9941980 Unicast packets 162620 64828 Non‑unicast packets 276 668 Discards 0 0 Errors 0 0 Unknown protocols 0 HELPING CAPTAIN CIAOCIAO AND BONNY BRAIN Ahoy there! Once upon a time, Captain CiaoCiao and Bonny Brain lent ye a hand with a certain matter we won’t speak of. And now, ye owe them a favor. But fear not, for it will be worth yer while to assist them on their latest venture. Join the daring duo and their loyal crew as they sail the seven seas, striking deals with unsa‑ vory characters across the globe. Their secret hideout is on the island of Baloo, where the currency of choice is Liretta. With a crew hailing from all corners of the world, all program outputs be in English, me hearties.

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6 DOI: 10.1201/9781003495550‑2 1Advanced String Processing After dealing with basic data types around characters and strings in another chapter, we will now discuss advanced string processing. The topics are formatted output, regular expressions, and string splitting. Prerequisites • Be able to format strings. • Be able to match, search, and replace with regular expressions. • Be able to split strings. • Understand character encodings and UTF‑8. Data types used in this chapter: • java.util.Formatter • java.lang.String • java.util.regex.Pattern • java.util.regex.Matcher • java.util.Scanner FORMAT STRINGS There are different ways in Java to format strings, numbers, and temporal data as a string. In the package java.text, you can find the classes MessageFormat, DateFormat, and DecimalFormat as well as the class Formatter and in String the method String.format(…). The next tasks can be solved using the formatting strings from Formatter in a rather easy way. Build ASCII Table ⭑ Bonny Brain has installed a new app on her Aye Phone that shows her the ASCII alphabet: $ ascii Usage: ascii [‑adxohv] [‑t] [char‑alias...] ‑t = one‑line output ‑a = vertical format ‑d = Decimal table ‑o = octal table ‑x = hex table ‑b binary table ‑h = This help screen ‑v = version information Prints all aliases of an ASCII character. Args may be chars, C \‑escapes, English names, ^‑escapes, ASCII mnemonics, or numerics in decimal/octal/hex.