1.3 Variables and Data Types
In this lesson, you will learn about variables and primitive data types in Java.
What is a Variable?
A variable is a name associated with a memory location in the computer, where you can store a value that can change or vary. For example, when you play a game, it will often have a score. Scores often start at 0 and increase, so they can change. A score can be stored in a variable.
Data Types
There are two types of variables in Java: primitive variables and object or reference variables. The primitive types on the AP Computer Science A exam are:
- int: represents integers (whole numbers) like 3, 0, -76, and 20393.
- double: represents non-integer numbers like 6.3, -0.9, and 60293.93032.
- boolean: represents only two values: true and false.
String is one of the object types on the exam and is the name of a class in Java. A String is written in a Java program as a sequence of characters enclosed in a pair of double quotes - like "Hello".
Declaring Variables in Java
To create a variable, you must tell Java its data type and its name. Creating a variable is also called declaring a variable. The syntax is:
dataType variableName;You can also initialize a variable when you declare it:
dataType variableName = initialValue;