Java Data Types

Java must be a specified data type:

int myNum = 5;               // Integer (whole number)
float myFloatNum = 5.99f;    // Floating point number
char myLetter = 'D';         // Character
boolean myBool = true;       // Boolean
String myText = "Hello";     // String

Data types are divided into two groups:

• Primitive data types – includes byte, short, int, long, float, double, boolean and char
• Non-primitive data types – such as String, Arrays and Classes (you will learn more about these in a later chapter)

Primitive Data Types

The size and type of variable values are specified by a primitive data type, which has no extra functions.

In Java, there are eight primitive data types:

Numbers

Primitive number types are divided into two groups:

Integer types stores whole numbers, positive or negative (such as 123 or -456), without decimals. Valid types are byte, short, int and long. Which type you should use, depends on the numeric value.

Floating point types represents numbers with a fractional part, containing one or more decimals. There are two types: float and double.

Despite the fact that Java has multiple numeric types, the most commonly used for numbers are int (for whole numbers) and double (for floating point numbers).
However, as you read on, we’ll go through each one in detail.

Integer Types

Byte

From -128 to 127, the byte data type can hold entire values.
When you know the value will be between -128 and 127, you can use this instead of int or other integer types to conserve memory:

Example

byte myNum = 100;
System.out.println(myNum);

Short

Theshort data type can store whole numbers from -32768 to 32767:

Example

short myNum = 5000;
System.out.println(myNum);

Int

Whole numbers between -2147483648 and 2147483647 can be stored in the int data type.
When creating variables with a numeric value, the int data type is the ideal data type in general and in our course. 

Example

int myNum = 100000;
System.out.println(myNum);

Long

From -9223372036854775808 to 9223372036854775807, the long data type can store entire numbers. When int is insufficient to store the value, this is utilized. It’s important to note that the value should conclude with a “L”:

Example

long myNum = 15000000000L;
System.out.println(myNum);

Floating Point Types

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

Float

The float data type can store fractional numbers from 3.4e−038 to 3.4e+038. Note that you should end the value with an “f”:

Example

float myNum = 5.75f;
System.out.println(myNum);

Double

The double data type can store fractional numbers from 1.7e−308 to 1.7e+308. Note that you should end the value with a “d”:

Example

double myNum = 19.99d;
System.out.println(myNum);

Is it better to use float or double?

The precision of a floating point value is the number of digits following the decimal point that the value can have.
The precision of float variables is just six or seven decimal digits, but the precision of double variables is around 15 digits.
As a result, for most calculations, it is safer to utilize double.

Scientific Numbers

A floating point number can also be a scientific number with an “e” to indicate the power of 10:

float f1 = 35e3f;
double d1 = 12E4d;
System.out.println(f1);
System.out.println(d1);

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

char myGrade = 'B';
System.out.println(myGrade);

char myVar1 = 65, myVar2 = 66, myVar3 = 67;
System.out.println(myVar1);
System.out.println(myVar2);
System.out.println(myVar3);

String greeting = "Hello World";
System.out.println(greeting);