Variable declarations

Variables are introduced in a program through variable declarations.

Variable declaration

Syntax:

type variableName;

• type is the type of the variable
  • for variables of type reference to an object it is the name of the class of which the object is an instance;
  • otherwise, it is a primitive predefined type - see Unit 4
• variableName is the name of the variable being declared

Semantics:

The declaration of a variable reserves a memory location for the variable and makes the variable available in the part of the program (block) where the declaration appears (more details in Unit 3). Notice that we have to declare a variable before we can use it.

Example:

String line;

• String is the type of the variable
• line is the name of the variable

After such a declaration, the variable line can be used in the program block in which the declaration appears (e.g., in the main() method, if the declaration appears there).

We can also declare several variables of the same type with a single declaration.

type variableName-1,...,variableName-n;

Such a declaration is equivalent to:

type variableName-1;
 ...
type variableName-n;