//Primitive Data Types
public class PrimitiveDataTypes {
int integer = 0;
boolean bool = true;
char character = 'a';
double doubleVal = 3.2;
}
public static void main(String[] args) {
PrimitiveDataTypes type = new PrimitiveDataTypes();
System.out.println(type.integer + 12);
System.out.println(type.doubleVal+2.2);
System.out.println(type.character);
}
main(null);
12
5.4
a
//Wrapper Classes
public class Wrappers {
Integer ageWrapper = 17;
int age = Integer.parseInt("17");
String gpaString = "3.9";
double gpaDouble = Double.parseDouble(gpaString);
}
public static void main(String[] args) {
Wrappers wrapper = new Wrappers();
System.out.println(wrapper.ageWrapper);
System.out.println(wrapper.age);
System.out.println(wrapper.gpaDouble);
}
main(null);
17
17
3.9
Enums
What are they?
Enums are a type of data, which allows a variable to be a predetermined set of values
Uses
- Examples: days of the week
Things you can do with Enums
- ordinal
- switch
- for loops
public class EnumTest {
enum Units {
PRIMITVE_DATA_TYPES,
CLASSES,
BOOLEAN,
ITERATION,
WRITING_CLASSES,
ARRAY,
ARRAY_LIST,
TWO_DIMENSIONAL_ARRAY,
INHERITANCE,
RECURSION;
}
public static void main(String[] args) {
System.out.println("What is the third unit in AP CSA? Answer: " + Units.BOOLEAN);
Units classUnit = Units.CLASSES;
System.out.println("What is the unit is Classes in AP CSA? Answer: " + (classUnit.ordinal() + 1));
Units selectedUnit = Units.ARRAY_LIST;
switch(selectedUnit) {
case PRIMITVE_DATA_TYPES:
System.out.println("The selected unit is: primitive data types");
break;
case BOOLEAN:
System.out.println("The selected unit is: boolean");
break;
case CLASSES:
System.out.println("The selected unit is: classes");
break;
case ITERATION:
System.out.println("The selected unit is: iteration");
break;
case WRITING_CLASSES:
System.out.println("The selected unit is: writing classes");
break;
case ARRAY:
System.out.println("The selected unit is: array");
break;
case ARRAY_LIST:
System.out.println("The selected unit is: array list");
break;
case TWO_DIMENSIONAL_ARRAY:
System.out.println("The selected unit is: 2d array");
break;
case INHERITANCE:
System.out.println("The selected unit is: inheritance");
break;
case RECURSION:
System.out.println("The selected unit is: recursion");
break;
}
for (Units allUnits: Units.values()) {
System.out.println(allUnits);
}
}
}
EnumTest.main(null);
What is the third unit in AP CSA? Answer: BOOLEAN
What is the unit is Classes in AP CSA? Answer: 2
The selected unit is: array list
Primitive_data_types
CLASSES
BOOLEAN
ITERATION
WRITING_CLASSES
ARRAY
ARRAY_LIST
TWO_DIMENSIONAL_ARRAY
INHERITANCE
RECURSION
Casting
Casting is converting one type of variable to another ex: double to int
public class Casting {
public static void main(String[] args) {
double castTest = 3.2;
System.out.println((int) castTest);
castTest = 3.7;
System.out.println((int) castTest);
System.out.println((int) (castTest+0.5));
int castTest2 = 3;
System.out.println(castTest2/2);
System.out.println(castTest2/2.0);
}
}
Casting.main(null);
What are the greatest values integers and doubles can store?
public class GreatestValue {
public static void main(String[] args) {
System.out.println(Integer.MAX_VALUE);
System.out.println(Integer.MIN_VALUE);
System.out.println(Double.MAX_VALUE);
System.out.println(Double.MIN_VALUE);
}
}
GreatestValue.main(null)
Assignment Operators Assignment operators are things like +=, -=, *=, %=
public class AssignmentOperators {
public static void main(String[] args) {
int firstInt = 9;
int secondInt = 1;
secondInt = firstInt+secondInt;
System.out.println(secondInt);
secondInt = 1;
secondInt += firstInt;
System.out.println(secondInt);
//Modulo
firstInt = 5;
secondInt = 3;
System.out.println(firstInt%secondInt);
System.out.println(firstInt%=3);
}
}
AssignmentOperators.main(null);
Hacks
import java.util.Scanner;
public class Calculator {
public static void main(String[] args) {
Scanner calcInput = new Scanner(System.in);
String input;
String num1;
String num2;
System.out.println("Pick your first number: ");
num1 = calcInput.nextLine();
System.out.println("Please input your desired calculator operation (+, -, *, /, %): ");
input = calcInput.nextLine();
System.out.println("Pick your second number: ");
num2 = calcInput.nextLine();
int numberInt1 = Integer.parseInt(num1);
int numberInt2 = Integer.parseInt(num2);
double numberDoub1 = Double.parseDouble(num1);
double numberDoub2 = Double.parseDouble(num2);
if( input.equals("+") ) {
int resultInt = numberInt1 + numberInt2;
double resultDoub = numberDoub1 + numberDoub2;
System.out.println("Integer: " + resultInt);
System.out.println("Double: " + resultDoub);
}
if( input.equals("-") ) {
int resultInt = numberInt1 - numberInt2;
double resultDoub = numberDoub1 - numberDoub2;
System.out.println("Integer: " + resultInt);
System.out.println("Double: " + resultDoub);
}
if( input.equals("*") ) {
int resultInt = numberInt1 * numberInt2;
double resultDoub = numberDoub1 * numberDoub2;
System.out.println("Integer: " + resultInt);
System.out.println("Double: " + resultDoub);
}
if( input.equals("/") ) {
int resultInt = numberInt1 / numberInt2;
double resultDoub = numberDoub1 / numberDoub2;
System.out.println("Integer: " + resultInt);
System.out.println("Double: " + resultDoub);
}
if( input.equals("%") ) {
int resultInt = numberInt1 % numberInt2;
double resultDoub = numberDoub1 % numberDoub2;
System.out.println("Integer: " + resultInt);
System.out.println("Double: " + resultDoub);
}
}
}
Calculator.main(null);
Pick your first number:
Please input your desired calculator operation (+, -, *, /, %):
Pick your second number:
Integer: 8
Double: 8.0
import java.util.Scanner;
public class Calculator {
public double add(double x, double y){
return x + y;
}
public double sub(double x, double y){
return x - y;
}
public double mult(double x, double y){
return x * y;
}
public double div(double x, double y){
if(y == 0){
System.out.println("Not possible");
return 0; // Return 0 to avoid proceeding with the division
}
return x / y;
}
public static void main(String[] args){
Calculator calculator = new Calculator();
Scanner sc = new Scanner(System.in);
while(true){
System.out.println("Choose an operation: 0. Exit, 1. Add, 2. Subtract, 3. Multiply, 4. Divide");
int choice = sc.nextInt();
if(choice == 0){
break;
}
System.out.println("Enter two numbers: ");
double num1 = sc.nextDouble();
double num2 = sc.nextDouble();
switch(choice){
case 1:
System.out.printf("You chose to add the two numbers %f and %f. Result: %f%n", num1, num2, calculator.add(num1, num2));
break;
case 2:
System.out.printf("You chose to subtract the two numbers %f and %f. Result: %f%n", num1, num2, calculator.sub(num1, num2));
break;
case 3:
System.out.printf("You chose to multiply the two numbers %f and %f. Result: %f%n", num1, num2, calculator.mult(num1, num2));
break;
case 4:
System.out.printf("You chose to divide the two numbers %f and %f. Result: %f%n", num1, num2, calculator.div(num1, num2));
break;
default:
System.out.println("Invalid choice!");
}
}
sc.close();
}
}
Calculator.main(null);
Choose an operation: 0. Exit, 1. Add, 2. Subtract, 3. Multiply, 4. Divide
Enter two numbers:
You chose to add the two numbers 2.000000 and 3.000000. Result: 5.000000
Choose an operation: 0. Exit, 1. Add, 2. Subtract, 3. Multiply, 4. Divide