Java Basics

Overview

This week we will learn the basics of Java, a programming language. This guide will walk you through how to write your first Java program as well as how to compile and run your code.

New Concepts

Printing on the Screen

System.out.println() is a Java statement that allows us to display messages on screen. For example:

> public static void main(String[] args) {
>    System.out.println("Hello World");
> }

Hello World

Mathematical Expressions

Java can be used to interpret basic mathematical expressions.

> 2 + 2
4
> 10 % 5
0

Assume A = 4 and B = 2

Operator	Name	Example
+	Addition	A + B = 6
-	Subtraction	A - B = 4
*	Multiplication	A * B = 8
/	Division	A / B = 2
%	Modulus	A % B = 0
++	Increment	A++ = 5
--	Decrement	A-- = 3

Data Types

In order to process data, computers need it to be organized by specific type. A word is different from a number and to determine the difference between the two we use data types to specify which one is which so we can process it accordingly. Java contains 8 primitive data types, primitive meaning that they are predefined in the language.

Of the 8, 4 deal with integer numbers and 2 deal with decimal numbers.

Integer Data Types

Integers are whole numbers that can be positive, negative, or zero. The main difference between the 4 integer types is the range of numbers you can use.

Type	Size	Range
long	64-bit	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 (-2^63 to 2^63 - 1)
int	32-bit	-2,147,483,648 to 2,147,483,647 (-2^31 to 2^31 - 1)
short	16-bit	-32,768 to 32,767 (-2^15 to 2^15 - 1)
byte	8-bit	-128 to 127 (-2^7 to 2^7 - 1)

int will probably be your most commonly used integer type. Just be aware that others exist as well.

Decimal Data Types

Double and float are the two data types that express decimal numbers like 3.14159. Again, the only difference between them is the range of numbers.

Type	Size	Range
double	64-bit	6-7 significant decimal digits
float	32-bit	15 significant decimal digits

char

The char data type holds characters. This basically means the alphabet: A-Z, a-z, etc. More specifically chars hold unicode characters which contain basically any and all written symbols.

boolean

Last but not least, the boolean data type. This can only hold one of two possible values: true or false. The default value of the data type is set to false.

String Concatenation

Storing Values in Variables

Let's Get Started - Put Everything Together!

Step 1:

TBA - figure out an exercise that uses every concept