Variables
Variable Declaration in Java
Used to declare a variable.
Syntax
modifier dataType variableName; //modifier is optional
//variables can be assigned values either separately or on declaration
variableName = value; //separate line assignment
modifier dataType variableName = value; //same line assignment
Notes
The modifier (public, private) restricts or permits direct access to the variable with respect to its scope (class, method, etc.).
Standard (non-static) variables declared within a class are called instance variables. Their value is attached to each class instance.
Variables without a modifier are known as local variables, typically used within a method. They are temporary and only exist within the scope of the where its declared method.
dataType is the data type of the variable. It can either be a primitive data type, or a String. Note that because a String is not a primitive data type, it must use same line assignment (with a value or with null) and cannot be modified after being assigned a value.
Example
public class Car {
private int speed; //public variable declaration
public int wheels; //private variable declaration
/*...constructor, etc...*/
public void speedUp() {
//local variable declaration, in line assignment, only seen within speedUp method
int speedIncrease = 10;
speed += speedIncrease;
}
}