Variables are containers that store data values.
In Java, there are different types of variables, for example:
- String — stores text, such as “Hello” and are surrounded by double quotes
- int — stores integers (whole numbers), without decimals, such as 225 or -225
- float — stores floating point numbers, with decimals, such as 20.20 or -20.20
- char — stores single characters, like ‘a’ or ‘B’ and are surrounded by single quotes
- boolean — stores values with two states: true or false
Non-primitive data types are called reference types because they refer to objects. The main difference between primitive and non-primitive data types are:
The byte data type can store whole numbers from -128 to 127 and can be used in place of other integer types when memory is a concern and there is a certainty that the value will be within the specified range.
The short data type can store whole numbers from -32768 to 32767.
The int data type can store whole numbers from -2147483648 to 2147483647. In general, the int data type is the preferred data type creating variables with a numeric value.
The long data type can store whole numbers from -9223372036854775808 to 9223372036854775807 when int is not large enough to store the value. The value should end with an “L”.
The float data type can store fractional numbers from 3.4e−038 to 3.4e+038 and should end with an “f”.
The double data type can store fractional numbers from 1.7e−308 to 1.7e+308 and should end with a “d”.
A floating-point number that includes an “e” to indicate the power of 10: float f1 = 35e3f.
A boolean data type is declared with the boolean keyword and can only take/return the values true or false.
The char data type is used to store a single character and must be surrounded by single quotes, like ‘A’ or ‘a’.
Additional information can be found below: https://www.w3schools.com/java/java_variables.asp