What is java variable ?
A variable is the name of a reserved area allocated in memory. It is a container which holds the value while the Java program is executed. A variable is assigned with a data type.
There Are 03 Types Of Variables In Java – (1) Local, (2) Instance And (3) Static
1) Local Variable
A variable declared inside the body of the method is called local variable. You can use this variable only within that method and the other methods in the class aren’t even aware that the variable exists. A local variable cannot be defined with “static” keyword.
2) Instance Variable
A variable declared inside the class but outside the body of the method, is called an instance variable. It is not declared as static. It is called an instance variable because its value is instance-specific and is not shared among instances.
3) Static variable
A variable that is declared as static is called a static variable. It cannot be local. You can create a single copy of the static variable and share it among all the instances of the class. Memory allocation for static variables happens only once when the class is loaded in the memory.
The rules to declare variables in Java :
- Java keywords cannot be used as variable names.
- Variable names are case-sensitive
- The first character must be a letter
How many Data Types in Java ?
Data types specify the different sizes and values that can be stored in the variable. There are two types of data types in Java – (1) primitive and (2) non-primitive.
1) Primitive data types – In Java language, primitive data types are the building blocks of data manipulation. There are 8 types of primitive data types –
- boolean (1 bit), byte (1 byte), char (2 byte), short (2 byte), int (4 byte), float (4 byte), long (8 byte) and double (8 byte).
2) Non-primitive data types – The non-primitive data types include Classes, Interfaces, and Arrays.