Variables and Data Types

Variables and Data Types

Understanding Variables

• A variable is like a container which holds information that can be modified or retrieved at any time in your Java program.
• Each variable has a data type which determines the size and layout of the variable’s memory, the range of values that can be stored and the set of operations that can be applied.
• The name of the variable is called an identifier. In Java, identifiers are case-sensitive.

Primitive Data Types

• Java has 8 primitive data types: byte, short, int, long, float, double, char and boolean.
• Numeric types include integer types (byte, short, int, long) and floating-point types (float, double).
• Character types include the char data type, used for storing Unicode characters.
• The boolean type has only two possible values: true or false; essentially used for logical operations.

Declaration, Initialization and Assignment

• In Java, before a variable is used, it must be declared with a statement that specifies its data type and name.
• Initialization is the process of assigning a value to a variable during its declaration.
• Assignment involves giving a variable value if not given during declaration; this is done with the use of the assignment operator (=).

Constant Variables

• A final keyword in Java is used to declare a constant variable. Its value can’t be modified.
• It’s a good practice to declare all letters of the identifier of a constant variable in uppercase.

Type Conversion and Casting

• Type conversion is a process of converting one primitive data type into another.
• Casting is a method of explicit conversion which involves converting a larger datatype into a smaller one or vice versa.