Book Image

Java Fundamentals

By : Gazihan Alankus, Rogério Theodoro de Brito, Basheer Ahamed Fazal, Vinicius Isola, Miles Obare
Book Image

Java Fundamentals

By: Gazihan Alankus, Rogério Theodoro de Brito, Basheer Ahamed Fazal, Vinicius Isola, Miles Obare

Overview of this book

Since its inception, Java has stormed the programming world. Its features and functionalities provide developers with the tools needed to write robust cross-platform applications. Java Fundamentals introduces you to these tools and functionalities that will enable you to create Java programs. The book begins with an introduction to the language, its philosophy, and evolution over time, until the latest release. You'll learn how the javac/java tools work and what Java packages are - the way a Java program is usually organized. Once you are comfortable with this, you'll be introduced to advanced concepts of the language, such as control flow keywords. You'll explore object-oriented programming and the part it plays in making Java what it is. In the concluding chapters, you'll get to grips with classes, typecasting, and interfaces, and understand the use of data structures, arrays, strings, handling exceptions, and creating generics. By the end of this book, you will have learned to write programs, automate tasks, and follow advanced courses on algorithms and data structures or explore more advanced Java courses.
Table of Contents (12 chapters)
Java Fundamentals


Classes that work with other classes in a generic way, like Vector, didn't have a way to explicitly tell the compiler that only one type was accepted. Because of that, it uses Object everywhere and runtime checks like instanceof and casting were necessary everywhere.

To solve this problem, Generic was introduced in Java 5. In this section you'll understand better the problem, the solution and how to use it.

What was the Problem?

When declaring an array, you tell the compiler what type of data goes inside the array. If you try to add something else in there, it won't compile. Look at the following code:

// This compiles and work
User[] usersArray = new User[1];
usersArray[0] = user;

// This wouldn't compile
// usersArray[0] = "Not a user";

/* If you uncomment the last line and try to compile, you would get the following error: */ error: incompatible types: String cannot be converted to User
        usersArray[0] = "Not a user";

Let's say you...