A Beginner's Guide Java Tutorial (OOPs Introduction - Object Oriented Programming (OOPs) in Java)

Simply put, variables are reserved memory locations where values can be stored. This indicates that you reserve memory space when you create a variable.
Based on a variable's data type, the operating system allocates memory and decides what can be stored there. All constants and variables defined for a given program must be described using one of the data types because the programming language in Java includes predefined definitions for each type of data (such as integer, character, hexadecimal, packed decimal, and so on).

the reserved memory As a result, you can store integers, strings, and numbers by assigning variables to various data types.

You can use decimals or characters in these variables.