# Variables and Types

Updated on Dec 22, 2021 by [Alan Morel](/content/alanmorel/index.html)

- [#java](/content/tag/java/index.html)

## Table of Contents

1. [Primitive Variable Types](/content/classes/java/variables-types#primitive-variable-types/index.html)
2. [Declaring](/content/classes/java/variables-types#declaring/index.html)
3. [Variable Naming Rules](/content/classes/java/variables-types#variable-naming-rules/index.html)

**Variables** are a fundamental part of any programming language, including [Java](/content/classes/java/index.html). Variables are used to store pieces of data and give them a name. When we want to use these variables in some way, we can refer to them by their name.

## Primitive Variable Types

Let's explore the **primitive types** of data that variables can hold.

- `String`: a string of characters, also known as text
- `byte`: a number between `-128` and `127`
- `short`: a number between `-32,768` and `32,767`
- `int`: a number between `-2,147,483,648` and `2,147,483,647`
- `long`: a number between -`9,223,372,036,854,775,808` to `9,223,372,036,854,775,807`
- `float`: a floating point number, a number with decimals
- `double`: a floating point number but with more precision
- `char`: a single character
- `boolean`: a binary value, `true` or `false`

Now that we know the primitive types supported in Java, let's declare our variables.

## Declaring

**Declaring** a variable is how you create them. Here's an example featuring all of the primitive data types:

```java
public class Main {
    public static void main(String[] args) {
        String a = "Sabe.io";
        System.out.println(a);

byte b = 6;
        System.out.println(b);

short c = 1337;
        System.out.println(c);

int d = 12345;
        System.out.println(d);

long e = 13371337;
        System.out.println(e);

float f = 13.37f;
        System.out.println(f);

double g = 13.37;
        System.out.println(g);

char h = 'a';
        System.out.println(h);

boolean i = true;
        System.out.println(i);
    }
}
```

```bash
Sabe.io
6
1337
12345
13371337
13.37
13.37
a
true
```

In general, to declare a variable, you must start off with their type, then an equal sign, then the value. This is the general syntax:

```java
type name = value;
```

Since Java is strongly typed, it requires you to give every variable their type.

## Variable Naming Rules

There are rules in place for naming Java variables, and here they are:

- The variable name can only contain alphanumeric characters, underscores, and dollar signs
- The variable name must start with a letter, dollar sign, or underscore
- The variable name cannot contain spaces

With that in mind, here are some examples of valid Java variable names:

```java
apples
_apples
_apples_
$apples
```

And here are some examples of invalid Java variables names:

```java
1apples
app les
&apples
%apples
```