Intro | Primitive Types | Reference Types | Stack and Heap | Code Example | Quiz |
Unit 1 - Primitive Types
Primitive Data Types
A primitive data type specifies the size and type of information. Primitive types are the simplest type of variables in Java. They simply store a small amount of data, according to the type. They are not associated with a class.
The 3 Primitive Data Types for College Board
There are eight primitive data types in Java, but only these 3 are used in AP CSA:
Data Type | Description |
---|---|
int | Stores whole numbers from -2,147,483,648 to 2,147,483,647 |
double | Stores decimal numbers. Sufficient for storing 15 decimal digits |
boolean | Stores true or false values |
To declare a variable, you write:
Type VariableName = Value;
For example:
int count = 0;
Variable Terms and Conventions
These are important items to remember with regards to Java and the College Board.
- A
variable name
is often referred to as thevariable identifier
in Java. - A
variable name
follows camel case conventions in Java (e.g., firstName). - A
class name
, which is a Data Type, follows Pascal case (e.g., BankAccount).
The 8 Primitive Data Types
Here is the complete list of primitive types in Java:
- byte: An 8-bit signed two’s complement integer.
- short: A 16-bit signed two’s complement integer.
- int: A 32-bit signed two’s complement integer.
- long: A 64-bit signed two’s complement integer.
- float: A single-precision 32-bit IEEE 754 floating point.
- double: A double-precision 64-bit IEEE 754 floating point.
- boolean: Stores either
true
orfalse
. - char: Stores a single 16-bit Unicode character.
Popcorn Hack: Greatest Value Terms
Primitive Data types have constraints
The program shows the constraints of Integers and Doubles. Define the following terms…
- constraints:
- overflow:
- underflow
public class GreatestValue {
public static void main(String[] args) {
System.out.println("Max Integer: " + Integer.MAX_VALUE);
System.out.println("Min Integer: " + Integer.MIN_VALUE);
System.out.println("Max Double: " + Double.MAX_VALUE);
System.out.println("Min Double: " + Double.MIN_VALUE);
// Integer Show Overflow
int i = Integer.MAX_VALUE;
i++;
System.out.println("Integer Max + 1, Overflow: " + i);
// Integer Show Underflow
int j = Integer.MIN_VALUE;
j--;
System.out.println("Integer Min - 1, Underflow: " + j);
// Integer Max + Min
int k = Integer.MAX_VALUE + Integer.MIN_VALUE;
System.out.println("Integer Max + Min: " + k);
}
}
GreatestValue.main(null);
Popcorn Hack: Fill in Data Type
The code below is broken….
- Fill in the blank, replace the underbars with the correct type.
- Output the contents to the Jupyter Terminal
___ zero = 0; //Whole number
___ pi = 3.14159; //Decimal values. Floating point numbers.
___ iAmTakingCSA = true; //Stores a true of false binary value
___ myProjectedGrad = 'A'; //Single character
___ iLoveCodeCodeCoding = "Yes"; //String of characters