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 .
Even though there are many numeric types in Java, the most used for numbers are int (for whole numbers) and double (for floating point numbers). However, we will describe them all as you continue to read.
Byte
The byte data type can store whole numbers from -128 to 127. This can be used instead of int or other integer types to save memory when you are certain that the value will be within -128 and 127:
Example
byte myNum = 100;
System.out.println(myNum);Short
The short data type can store whole numbers from -32768 to 32767:
Example
short myNum = 5000;
System.out.println(myNum);Int
The int data type can store whole numbers from -2147483648 to 2147483647. In general, and in our tutorial, the int data type is the preferred data type when we create variables with a numeric value.
Example
int myNum = 100000;
System.out.println(myNum);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":
Example
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);Use float or double ?
The precision of a floating point value indicates how many digits the value can have after the decimal point. The precision of float is only 6-7 decimal digits, while double variables have a precision of about 16 digits.
Therefore it is safer to use double for most calculations.
Scientific Numbers
A floating point number can also be a scientific number with an "e" to indicate the power of 10:
Example
float f1 = 35e3f;
double d1 = 12E4d;
System.out.println(f1);
System.out.println(d1);