Learning Java Fundamentals: Variables

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Variables

In programming, variables are usually used for data storage. In Java, there are different types of variables:

String ~ stores text surrounded by double quotes, such as “Friend”

int ~ stores whole number integers — excluding decimals, such as 300 or -300

float ~ stores decimal, or floating point numbers such as 23.55 or -23.55

char ~ stores single characters, such as ‘d’ or ‘C’

boolean ~ stores truthy or falsey values

Declaring Variables

When declaring a variable in Java, we must first specify the type of variable it is and then assign the value with a unique name:

type variableName = value;
String myName = "Ifeoluwa";
int myAge = 100;
float decimal = 0.03;
char letter = 'g';
boolean imHappy = true;

A variable can also be declared before assigning it a value!

int wholeNumber; //declared first
wholeNumber = 6; //then assigned

Values stored in variables can be overwritten with new values.

int wholeNumber; //declared first
wholeNumber = 6; //then assigned
wholeNumber = 7; //new value
sidenote: to keep a variable from being overwritten use the keyword final. This declares the variable as constant, or unchangeable

Declaring Multpile Variables

To declare variables of the same type, commas are utilized like so:

int x = 8, y = 9, z = 10;
System.out.println(x + y + z);

Can also assign the same value to multiple variables — of the same type:

String name, noun, text;
name = noun = text = "Ifeoluwa ";
System.out.println(name + noun + text); // Ifeoluwa Ifeoluwa Ifeoluwa what will print on to the screen

Print Variables

The statement System.out.println() is used to print code on to the screen. It is also utilized to print varaibles:

String myName = "Ifeoluwa";
System.out.println(myName); // Ifeoluwa what will print on to the screen

To add text, use + character

System.out.println("Hello " + myName); // Hello Ifeoluwa what will print on to the screen

Can also combine variables together and store them in to another variable:

String myFirstName = "Ifeoluwa ";
String myLastName = "Akinremi Wade";
String myFullName = myFirstName + myLastName
System.out.println(myFullName); // Ifeoluwa Akinremi Wade what will execute on to the screen

The + characters works for mathematical values as well

int x = 5;
int y = 6;
System.out.println(x + y); // // 11 what will print on to the screen