Variables store values. They are the most basic entity used to store data such as text, numbers, etc. in a program.
In <ahref='https://github.com/FreeCodeCamp/FreeCodeCamp/wiki/Java'target='_blank'rel='nofollow'>Java</a>, variables are <ahref='https://en.wikipedia.org/wiki/Strong_and_weak_typing#Definitions_of_.22strong.22_or_.22weak.22'target='_blank'rel='nofollow'>_strongly typed_</a>, which means you have to define the type for each variable whenever you declare it. Otherwise, the compiler will throw an error at <ahref='https://en.wikipedia.org/wiki/Compile_time'target='_blank'rel='nofollow'>compile time</a>. Therefore, each variable has an associated '<ahref='https://guide.freecodecamp.org/java/data-types'target='_blank'rel='nofollow'>data-type</a>' of one of the following:
* Reference Type: `String`, `StringBuilder`, `Calendar`, `ArrayList`, etc.
You may have noticed that the **Wrapper Type** consists of types spelled exactly like the **Primitive Type**, except for the capitalised alphabet in the begining (like the **Reference Type**). This is because the Wrapper Types are actually a part of the more general Reference Types, but <i>closely linked</i> with their primitive counterparts via <ahref='https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html'target='_blank'rel='nofollow'>autoboxing and unboxing</a>. For now, you just need to know that such a 'Wrapper Type' exists.
Typically, you can <i>declare</i> (i.e., create) variables as per the following syntax: <<i>data-type</i>> <<i>variableName</i>>;
```java
// Primitive Data Type
int i;
// Reference Data Type
Float myFloat;
```
You can <i>assign</i> a value to the variable either simultaneously when you are declaring it (which is called <i>initialisation</i>), or anywhere in the code after you have declared it. The symbol **=** is used for the same.
```java
// Initialise the variable of Primitive Data Type 'int' to store the value 10
int i = 10;
double amount = 10.0;
boolean isOpen = false;
char c = 'a'; // Note the single quotes
//Variables can also be declared in one statement, and assigned values later.
int j;
j = 10;
// initiates an Float object with value 1.0
// variable myFloat now points to the object
Float myFloat = new Float(1.0);
//Bytes are one of types in Java and can be
//represented with this code
int byteValue = 0B101;
byte anotherByte = (byte)0b00100001;
```
As evident from the above example, variables of Primitive type behave slightly differently from variables of Reference (& Wrapper) type - while Primitive variables <i>store</i> the actual value, Reference variables <i>refer to</i> an 'object' containing the actual value.
