Book Image

Java Coding Problems - Second Edition

By : Anghel Leonard
Book Image

Java Coding Problems - Second Edition

By: Anghel Leonard

Overview of this book

The super-fast evolution of the JDK between versions 12 and 21 has made the learning curve of modern Java steeper, and increased the time needed to learn it. This book will make your learning journey quicker and increase your willingness to try Java’s new features by explaining the correct practices and decisions related to complexity, performance, readability, and more. Java Coding Problems takes you through Java’s latest features but doesn’t always advocate the use of new solutions — instead, it focuses on revealing the trade-offs involved in deciding what the best solution is for a certain problem. There are more than two hundred brand new and carefully selected problems in this second edition, chosen to highlight and cover the core everyday challenges of a Java programmer. Apart from providing a comprehensive compendium of problem solutions based on real-world examples, this book will also give you the confidence to answer questions relating to matching particular streams and methods to various problems. By the end of this book you will have gained a strong understanding of Java’s new features and have the confidence to develop and choose the right solutions to your problems.
Table of Contents (16 chapters)
1
Text Blocks, Locales, Numbers, and Math
Free Chapter
2
Objects, Immutability, Switch Expressions, and Pattern Matching
14
Other Books You May Enjoy
15
Index

117. Handling map capacity

Let’s assume that we need a List capable of holding 260 items. We can do it as follows:

List<String> list = new ArrayList<>(260);

The array underlying ArrayList is created directly to accommodate 260 items. In other words, we can insert 260 items without worrying about resizing or enlarging the list several times in order to hold these 260 items.

Following this logic, we can reproduce it for a map as well:

Map<Integer, String> map = new HashMap<>(260);

So, now we can assume that we have a map capable of accommodating 260 mappings. Actually, no, this assumption is not true! A HashMap works on the hashing principle and is initialized with an initial capacity (16 if no explicit initial capacity is provided) representing the number of internal buckets and a default load factor of 0.75. What does that mean? It means that when a HashMap reaches 75% of its current capacity, it is doubled in size and a rehashing...