Data types define the values a variable can hold in its lifetime. There are basically two types of data types available in Java:
- Primitive data types: Primitive data types are the most basic data types that hold a scalar value. It includes boolean, char, short, int, byte, long, float, and double.
- Non-primitive (Reference) data types: Non-primitive data types are created by programmers that hold an object. It includes Arrays, Classes, and Interfaces.
List of 8 primitive data types with their byte size and default value:
| Data Type | Size(in Bytes) | Default Value |
|---|---|---|
| byte | 1 | 0 |
| short | 2 | 0 |
| int | 4 | 0 |
| long | 8 | 0 |
| float | 4 | 0.0 |
| double | 8 | 0.0 |
| char | 2(UNICODE) | '\u0000' |
| boolean | depend on JVM | false |
- The formula for Signed data type: -2n-1 to 2n-1-1
- The formula for Unsigned data type: 0 to 2n-1
- All integer and floating-point data types are Signed.
- All character data type is unsigned.
Byte data type: Byte data type value range between -128 to 127. Its default value is 0 and the minimum value it can hold is -128 and the maximum value it can hold is 127. It is used to store the value when memory saving is the most important requirement.
Example: byte x = 5;
Short data type: Short data type values range between -32,768 to 32,767 and its default value is also 0. It is used to save the memory just like a byte data type.
Example: short x = 2000;
Int data type: Int data type values range between -231 to 231-1 and its default value is 0. It is used to store integer types of data whose value is there in the given range.
Example: int a = 234534;
Long data type: Long data type values range between -263 to 263-1 and its default value is 0. It is used when values go out of the integer range.
Example: long a = 100000L;
Float data type: Float data type values range is unlimited and used to store floating-point number values. It is preferred to use a float data type instead of double when saving memory is important. Its default value is 0.0F.
Example: float a = 130.0f;
Double data type: Double data type values range is also unlimited and like float, it is also used to store decimal type values. Its default value is 0.0d.
Example: double a = 23.4;
Char data type: Char data type values are a single 16-bit Unicode character use to store characters. Its range is between '\u0000' to '\uffff'.
Example: char ch = 'A';
Reference data types.
A reference variable can be used to refer to any object of the declared type or any compatible type. The value of any reference variable is null.
Example: Employee emp = new Employee();
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