Declaring Variables

Common Data Types

Four common types are described here.

More information on boolean can be found here.

NOTE WELL -- Java is case sensitive. In other words Java expects "String" and not "string", and "int" and not "INT", etc.

String - e.g., "Hello World", "Asha Johansson"
int - (integer) e.g., -10, 0, -1, 972722
boolean - e.g., true or false (constrained to only one of these two values) -- Also see Boolean
double - e.g., -25.392, 0.5, 0.00001, 10.0

Example 1

Here we declare six variables.

We'll break this down in the following steps.

String firstName;
int width;
int treeDiameter;
String description;
boolean isLarge;
double diagonalLength;

Example - Line 1

See the highlighted line.

The first token (String) is the data type.
The second token (firstName) is the name of the variable
The first token (String) must be spelled to exactly match the actual data type
The second (firstName) is the variable name (coder's choice -- as long as it has a valid name)
The other lines are declared similarily (data type followed by variable name)

String firstName;
int width;
int treeDiameter;
String description;
boolean isLarge;
double diagonalLength;

Example - Line With Boolean

See the highlighted line.

The first token (boolean) is the data type.
The second token (isLarge) is the name of the variable
The first token (boolean) must be spelled to exactly match the actual data type
The second token (isLarge) is the variable name (coder's choice -- as long as it has a valid name)
The other lines are declared similarily (data type followed by variable name)

String firstName;
int width;
int treeDiameter;
String description;
boolean isLarge;
double diagonalLength;