Understanding Java Basics – Variables, Data Types and Operators

Hello everyone,

I am currently learning Java programming and would like to share some basic concepts that beginners should understand.

1. Variables
A variable is used to store data in a program. In Java, we must declare the variable with a data type.

Example:

int number = 10;
String name = "Sabari";

2. Data Types
Java has different types of data types such as:

int – used to store integers

double – used to store decimal numbers

char – used to store a single character

String – used to store text

Example:

int age = 20;
double price = 99.99;
char grade = 'A';
String city = "Madurai";

3. Operators
Operators are used to perform operations on variables.

Common operators:

Arithmetic: + - * /

Relational: == != > <

Logical: && ||

Example:

int a = 5;
int b = 3;
int sum = a + b;
System.out.println(sum);

Conclusion
Learning these basics helps beginners understand Java programming better before moving to advanced topics like loops, arrays, and object-oriented programming.

Thank you!

Madhumitha Moorthy wrote:. . . A variable is used to store data in a program. In Java, we must declare the variable with a data type.

Those are fields. Fields are used to store data in a program, but it is possible to store data other ways, e.g. writing them to files. There are also local variables, which have data for use in a method, but disappear when the method completes, Fields need to be declared with a specific type, but local variables can (and probably shoulm whenever possible) be declared with var.  Example:-var number = 10; // local variables only (both lines) var name = "Campbell";

. . . Java has different types of data types  . . .

Nearly every class anybody created with the intention of instantiating that class becomes a datatype, so there are almost unlimited numbers of different datatypes. Those you named are only a few of the commonest types.
A double isn't a decimal fraction. It is a number probably with a fractional part, denominated in binary and occupying 64 bits. I don't have enough time to discuss the exact conventions in its format.

. . . Operators are used to perform operations on variables. . . .

Yes The operators && and || are called conditional operators in the Java® Language Specification (=JLS)←Link.

Learning these basics helps beginners understand Java programming better before moving to advanced topics like loops, arrays, and object-oriented programming. . . .

I have my own opinions, and many people will disagree with me. But I think learning what an object is, and what a field is, are fundamental to object‑oriented programming, and object‑oriented programming is more basic than loops and arrays, and should be taught first.

Campbell, I think the original poster may not have gotten to classes yet, in which case the distinction between local variables and fields isn't going to mean much.  I suspect the poster is talking about local variables, but will learn about var a little later, as a modification to what was already learned.  If I'm right, then saying "those are fields" will just cause confusion.

I meant that the things used to store information are called fields, not that what we were shown are fields.

A local variable stores information too - even if it may be more short-term than storage in a field.  There is still data being stored on the stack.  JLS 4.12 agrees:

4.12. Variables
A variable is a storage location and has an associated type, sometimes called its compile-time type, that is either a primitive type (§4.2) or a reference type (§4.3).