Book Image

The Java Workshop

By : David Cuartielles, Andreas Göransson, Eric Foster-Johnson
4 (2)
Book Image

The Java Workshop

4 (2)
By: David Cuartielles, Andreas Göransson, Eric Foster-Johnson

Overview of this book

Java is a versatile, popular programming language used across a wide range of industries. Learning how to write effective Java code can take your career to the next level, and The Java Workshop will help you do just that. This book is designed to take the pain out of Java coding and teach you everything you need to know to be productive in building real-world software. The Workshop starts by showing you how to use classes, methods, and the built-in Collections API to manipulate data structures effortlessly. You’ll dive right into learning about object-oriented programming by creating classes and interfaces and making use of inheritance and polymorphism. After learning how to handle exceptions, you’ll study the modules, packages, and libraries that help you organize your code. As you progress, you’ll discover how to connect to external databases and web servers, work with regular expressions, and write unit tests to validate your code. You’ll also be introduced to functional programming and see how to implement it using lambda functions. By the end of this Workshop, you’ll be well-versed with key Java concepts and have the knowledge and confidence to tackle your own ambitious projects with Java.
Table of Contents (20 chapters)

Predicate Interface

The predicate interface is a quite simple, yet surprisingly elegant and complex, functional interface that allows you, as a programmer, to define functions that describe the state of your program in the shape of Booleans. In Java, speech predicates are one-argument functions that return a Boolean value.

The predicate API looks like this:

boolean test(T t);

However, the predicate API also utilizes the new interface features of Java 8. It supports default and static functions to enrich the API, allowing more complex descriptions of your program's state. Here, three functions are important:

Predicate<T> and(Predicate<T>);
Predicate<T> or(Predicate<T>);
Predicate<T> not(Predicate<T>);

With these three functions, you can chain predicates to describe more complex queries on your program's state. The and function will combine two or more predicates, ensuring that every predicate supplied returns true.