Java data types tell the compiler what kind of value a variable can store and how much memory it needs.

Data types in Java

Data types are divided into two groups: primitive data types and non-primitive data types.

• Primitive data types include byte, short, int, long, float, double, boolean, and char.
• Non-primitive data types include String, Arrays, and Classes.

Primitive data types and sizes

• byte - 1 byte
• short - 2 bytes
• int - 4 bytes
• long - 8 bytes
• float - 4 bytes
• double - 8 bytes
• boolean - 1 bit
• char - 2 bytes

Byte

The byte data type can store whole numbers from -128 to 127.

byte myNum = 100;

System.out.println(myNum);

Short

The short data type can store whole numbers from -32768 to 32767.

short myNum = 5000;

System.out.println(myNum);

Integer

The int data type can store whole numbers from -2147483648 to 2147483647. It can store whole numbers.

Example: int a = 10;

Long

The long data type can store whole numbers from -9223372036854775808 to 9223372036854775807.

This is used when int is not large enough to store the value. Note that you should end the value with an L.

long myNum = 15000000000L;

System.out.println(myNum);

Floating Point Types

You should use a floating point type whenever you need a number with a decimal, such as 9.99 or 3.14515.

The float and double data types can store fractional numbers. Note that you should end the value with an f for floats and d for doubles.

Float Example

float myNum = 5.75f;

System.out.println(myNum);

Double Example

double myNum = 19.99d;

System.out.println(myNum);

Boolean

Java has a boolean data type, which can only take the values true or false.

boolean isJavaFun = true;
boolean isFishTasty = false;

System.out.println(isJavaFun);     // Outputs true
System.out.println(isFishTasty);   // Outputs false

Characters

The char data type is used to store a single character. The character must be surrounded by single quotes, like 'A' or 'c'.

char myGrade = 'B';

System.out.println(myGrade);

Non-Primitive Data Types

Non-primitive data types are called reference types because they refer to objects.

Examples of non-primitive types are Strings, Arrays, Classes, Interface, etc.