Java Basics Lesson 1 - Variables and Data Types

All major programming languages use this simple concept, so what you learn here can be taken to almost any modern programming language.

Variables and Literals

Variables are dynamic and can be changed. Variables basically hold data or information. Think of them as  slots in a memory bank.  Variables can be assigned values easily and they hold that data until they are changed or discarded as redundant.

A literal is a fixed type of data (the types of data that can be stored in a variable).  There are four types of literals. These are:

1. Booleans (True or false)
2. Characters and Strings (character is a single letter, Strings consist of usually more than one character)
3. Numbers (Java supports integer, floating point, byte literals)
4. Nulls (The Null literal is literally what it means...nothing)

Examples of all above:

boolean hairywoman = true;

char initial = p;

String surname = "rabbids";

int integer = 3;

float floating = 3.1467788557757785464434 ; (floats can hold 32 bits of data)

double mega_floating = 3.4e+038; (doubles can contain up to 64 bits of data)

byte byte_literal = 2; (nobody really uses bytes anymore as integers do the same job)

When we are coding we will often need to hold information that a method or part of the program will require to use later. Variables do this efficiently. You can use them in multiple ways to achieve a goal for example.....

int a = 5; 

int b = 3;

int result = a + b;

the result variable now holds an integer 8.... clever stuff!

you could then use a boolean in a loop (we will get to loops later)

if (result == 8 )

{

    boolean answer = true;

}

else

{

   boolean answer = false;

}


Thats all there is to it folks!