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Java Fundamentals
Java Fundamentals

Java Fundamentals: A fast-paced and pragmatic introduction to one of the world's most popular programming languages

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Java Fundamentals

Chapter 2. Variables, Data Types, and Operators

Note

Learning Objectives

By the end of this lesson, you will be able to:

  • Use primitive data types in Java

  • Use reference types in Java

  • Implement simple arithmetic operations

  • Use type-casting methods

  • Input and output various data types

Introduction


In the previous lesson, we were introduced to the Java ecosystem and the tools that are needed to develop Java programs. In this lesson, we will start our journey of the Java language by looking at the fundamental concepts in the language such as variables, data types, and operations.

Variables and Data Types


One of the fundamental concepts in computer programming is memory, used to store information in the computer. Computers use bits as the smallest information that can be stored. A bit is either a 1 or 0. We can group 8 bits to get what is called a byte. Because bits are very small, we usually deal with bytes as the smallest unit when programming. When we write programs, what we are essentially doing is fetching some bits from a certain memory location, doing some operations on them, and writing back the result to a memory location.

We need a way to store different kinds of data in the computer's memory and tell the computer what kind of data is stored at what memory location.

Data types are a way for us to specify what kind of data and the size we need to store at a given memory location. An example of a data type is an integer, a character, or a string. Broadly, the data types available in Java can be classified into the following types:

  • Primitive data types

  • Reference...

Integral Data Types


Integral types are types that have integer values. These are int, long, short, byte, and char.

int Data Type

The int data type is used to represent integers. Integers are 32-bit numbers in the range of -2,147,483,648 to 2,147,483,647. Example of integers are 0, 1, 300, 500, 389 230, 1,345,543, -500, -324,145, and others in that range. For example, to create an int variable to hold a value 5, we write the following:

int num = 5;

The num variable is now an int with a value of five. We can also declare more than one variable of the same type in one line:

int num1, num2, num3, num4, num5;

Here, we have created five variables, all of the int type, and initialized to zero. We can also initialize all of the variables to a specific value, as follows:

int num1 = 1, num2 = 2, num3 = 3, num4 = 4, num5 = 5;

In addition to expressing integers in decimal format, we can also express integers in octal, hexadecimal, and binary format:

As a summary of the aforementioned four formats of representing...

Type Casting


To convert an int of value of 23 into a long literal, we would need to do what is called type casting:

int num_int = 23;
long num_long = (long)num_int;

In the second line, we cast the num_int of the int type to a long literal by using the notation (long)num_int. This is referred to as casting. Casting is the process of converting one data type into another. Although we can cast a long to an int, remember that the number might be outside the int range and some numbers will be truncated if they can't fit into the int.

As is with int, long can also be in octal, hexadecimal, and binary, as shown in the following code:

long num = 117L;
long hex_num = 0x75L;
long oct_num = 0165L;
long bin_num = 0b1110101L;

Exercise 5: Type Casting

It's often important to change one type to another. In this exercise, we will convert an integer into a floating point:

  1. Import Scanner and create a public class:

    import java.util.Scanner;
     
    public class Main
     
    { 
        static Scanner sc = new Scanner(System.in);...

Summary


In this lesson, we learned about the use of primitive and reference data types, along with simple arithmetic operations on data in Java. We learned how to cast data types from one type to another. We then saw how we can work with floating-point data types.

In the next lesson, we will work with conditional statements and looping structures.

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Key benefits

  • Get introduced to Java, its features, and its ecosystem
  • Understand how Java uses object-oriented programming
  • Become an expert Java exception handler

Description

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.

Who is this book for?

Java Fundamentals is designed for tech enthusiasts who are familiar with some programming languages and want a quick introduction to the most important principles of Java.

What you will learn

  • Create and run Java programs
  • Use data types, data structures, and control flow in your code
  • Implement best practices while creating objects
  • Work with constructors and inheritance
  • Understand advanced data structures to organize and store data
  • Employ generics for stronger check-types during compilation
  • Learn to handle exceptions in your code

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Mar 15, 2019
Length: 408 pages
Edition : 1st
Language : English
ISBN-13 : 9781789801736
Vendor :
Oracle
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Product Details

Publication date : Mar 15, 2019
Length: 408 pages
Edition : 1st
Language : English
ISBN-13 : 9781789801736
Vendor :
Oracle
Category :
Languages :

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Table of Contents

9 Chapters
Introduction to Java Chevron down icon Chevron up icon
Variables, Data Types, and Operators Chevron down icon Chevron up icon
Control Flow Chevron down icon Chevron up icon
Object-Oriented Programming Chevron down icon Chevron up icon
OOP in Depth Chevron down icon Chevron up icon
Data Structures, Arrays, and Strings Chevron down icon Chevron up icon
The Java Collections Framework and Generics Chevron down icon Chevron up icon
Advanced Data Structures in Java Chevron down icon Chevron up icon
Exception Handling Chevron down icon Chevron up icon

Customer reviews

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Mr. Matthew J. Barnard Jul 03, 2021
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This book is incredibly cheaply made. The fonts are terrible, with severe printing problems on the code example font, where they are unreadable. There has clearly been zero quality control and care taken on the production of the book. I feel sorry for the author.At this price, I was expecting something close O'Reilly quality in terms of print. I'm shocked that it's not even usable. I'm returning the book.
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