☕ Java Data Types and Variables Explained

In Java, variables are containers for storing data values, and each variable has a data type that tells Java what kind of data it holds.

🧩 Java Data Types

Java has two main categories of data types:

1. Primitive Data Types (built-in)

These are the most basic types in Java. There are 8 primitive data types:

Data Type Size Description Example

byte 1 byte Small integer (-128 to 127) byte a = 100;

short 2 bytes Larger than byte (-32K to 32K) short b = 20000;

int 4 bytes Default for integers int c = 100000;

long 8 bytes Very large integers long d = 123456789L;

float 4 bytes Decimal numbers (less precision) float e = 5.75f;

double 8 bytes Decimal numbers (more precision) double f = 19.99;

char 2 bytes Single character char g = 'A';

boolean 1 bit True or false boolean h = true;

2. Non-Primitive (Reference) Data Types

These refer to objects and include:

String

Arrays (int[], String[], etc.)

Classes

Interfaces

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String name = "Alice";

int[] numbers = {1, 2, 3};

📦 Declaring Variables in Java

Syntax:

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dataType variableName = value;

Examples:

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int age = 25;

double price = 19.99;

char grade = 'A';

boolean isJavaFun = true;

You can also declare multiple variables of the same type:

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int x = 1, y = 2, z = 3;

🎯 Variable Types in Java

Type Scope/Usage Example

Local Inside a method void method() { int a = 10; }

Instance Inside a class, but outside methods int age; (used by objects)

Static Shared across all instances (use static) static int count;

✅ Best Practices

Use meaningful variable names: userAge, not x

Choose the smallest data type that fits your needs

Use final if the value shouldn’t change:

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final double PI = 3.14159;

🔚 Summary

Java has 8 primitive types and many non-primitive types

Every variable must be declared with a data type

Choose the right type for efficiency and clarity

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