- All code that runs must be in the main method
- Data types are different categories in which one can store various types of data. The main Primitve data types are: Integer (int): used for whole numbers Double (double): used for numbers with decimals Boolean (boolean): used for true or false conditionals For Primitive types, variables store actual data instead of reference If the variable is declared final, it cannot be edited A non Primitive type which is commonly used is String Stores text
- To comment your code, use // for single line comments and /**/ for multiple lines
- In order to perform mathmatical calculations on integers and doubles, you can use operators
- Main ones are +, -, *, /
- Modulus is %, used to get remainder when two numbers are divided
Example
public class Math {
public static void main(String[] args) {
int number = 2;
int number2 = 5;
double number3 = 2.0;
double number4 = 5.0;
System.out.println(number+number2);
System.out.println(number3+number4);
System.out.println(number-number2);
System.out.println(number3-number4);
System.out.println(number * number2);
System.out.println(number3 * number4);
System.out.println(number/number2);
System.out.println(number3/number4);
System.out.println(number4 % number3);
System.out.println(number2 % number);
}
}
Math.main(null);
Compute the remainder of 6 multiplied by 1234124 divided by 11345 minus 890809 plus 90800 (use order of operations) is divided by 980098, and store this in a variable called num (get an exact number as opposed to a whole number)
public class Cast {
public static void main(String[] args) {
double num = 10.5;
int num2 = 100;
int numInt = (int)num;
double num2Double = (double)num2;
System.out.println(num);
System.out.println(num2);
System.out.println(numInt);
System.out.println(num2Double);
System.out.println(Integer.MAX_VALUE);
System.out.println(Integer.MIN_VALUE);
}
}
Cast.main(null);
Assignment Operators
- += adds value of a variabe to another variable and assigns total value to first variable
- -= subtracts value of a variabe to another variable and assigns total value to first variable
- *= multiplies value of a variabe to another variable and assigns total value to first variable
- /= multiplies value of a variabe to another variable and assigns total value to first variable
- %= takes the remainder of a variable with a second variable and assigns remainder to first variable
- ++ increments a variable by 1, to incrememt by more change second plus to number which you want to incrememnt by
- -- subracts a variable by 1, to incrememt by more change second plus to number which you want to subtract by
int myInt = 9;
double myDouble = myInt; // Automatic casting: int to double
System.out.println(myInt); // Outputs 9
System.out.println(myDouble); // Outputs 9.0
import java.lang.Math;
public class Program {
public static void main(String[] args) {
double test1 = 1.234;
double test2 = -1.567;
// ... Math.floor will always go towards negative infinity.
System.out.println(Math.floor(test1));
System.out.println(Math.floor(test2));
// ... Math.round may go towards negative or positive infinity.
System.out.println(Math.round(test1));
System.out.println(Math.round(test2));
// ... Casting to int will remove the fractional part.
// This truncates the number.
System.out.println((int) test1);
System.out.println((int) test2);
}
}
public class Printing {
public static void main(String[] args){
System.out.println("Kian Pasokhi");
System.out.println("Period 2");
}
}
Printing.main(null);
public class Biodata {
public static void main(String[] args) {
String name = "Kian Pasokhi";
int age = 17;
boolean underclassman = false;
double height = 5.7;
System.out.println(name);
System.out.println(age);
System.out.println(underclassman);
System.out.println(height);
}
}
Biodata.main(null);
public class Num {
public static void main(String[] args) {
double num = ( ( 123 * 15003 ) / 11345 );
System.out.println(num);
}
}
Num.main(null);
public class Operators {
public static void main(String[] args) {
long num = 23948294;
num %= 4;
System.out.println("Remainder when divided by 4 is " + num);
}
}
Operators.main(null);
public class CastActivity {
public static void main(String[] args) {
double dNum = 123456.123456;
int dInt = (int) dNum;
System.out.println("the double to the integer is: " + dInt);
}
}
CastActivity.main(null);
public class Main {
public static void main (String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("What is your name?");
String name = sc.next(); //string
System.out.println(name);
System.out.println("How many pizzas do you want to buy?");
int pizzas = sc.nextInt(); //integer
System.out.println(pizzas);
System.out.println("Do you have the discount (true/false)?");
boolean hasDiscount = sc.nextBoolean(); //boolean
System.out.println(hasDiscount);
double price; //double, defaults to 0
if (hasDiscount) {
price = 1.20;
} else {
price = 2.10;
}
char firstChar = name.charAt(0); //character
double finalPrice = price * pizzas * 1.08; // adding taxes
System.out.println("Hi " + firstChar + "! You have to pay " + (finalPrice) + " dollars.");
}
}
Main.main(null);
import java.util.Scanner;
import java.lang.Math;
public class GradeCalculator {
private String category;
private double current;
private double percent;
private double desired;
private double test;
private double percent_test;
private double current_test;
private int points_test;
private int points_final;
public double calculate() {
this.enterCat();
if (category.equals("separate")) {
this.enterVals();
// current * (1-percent) + final * percent = desired
test = (desired - (current * (1-percent/100))) / (percent/100); // Ex. 95 - (90 * (1 - .20)) / .20
}
else if (category.equals("tests")) {
this.enterPoints();
// current_points = current * 100 - percent_test * points_test
// percent_test * (points_test + points_final) + (1-percent_test) * (current_points) = desired
percent_test /= 100;
int current_points = (int)current - (int)(percent_test) * points_test;
test = ((desired - ((1-percent_test)*current_points)/percent_test) - points_test);
}
return test;
}
private void enterCat() {
while (true) {
Scanner dd = new Scanner(System.in);
System.out.print("Enter final category (separate/tests): ");
try {
category = dd.nextLine();
System.out.println(category);
break;
} catch (Exception e) { // catch non-numerical input
System.out.println("Not a string, " + e);
}
dd.close();
}
}
private void enterVals() {
while (true) {
Scanner dd2 = new Scanner(System.in);
try {
System.out.print("Current grade: ");
current = dd2.nextDouble();
System.out.println(current);
System.out.print("Percentage of grade that is final: ");
percent = dd2.nextDouble();
System.out.println(percent);
System.out.print("Desired grade: ");
desired = dd2.nextDouble();
System.out.println(desired);
break;
} catch (Exception e) { // catch non-numerical input
System.out.println(current + "not a double, " + e);
}
dd2.close();
}
}
private void enterPoints() {
while (true) {
Scanner dd3 = new Scanner(System.in);
try {
System.out.print("Current grade: ");
current = dd3.nextDouble();
System.out.println(current);
System.out.print("Percentage of grade that is tests: ");
percent = dd3.nextDouble();
System.out.println(percent_test);
System.out.print("Current percent in tests: ");
current_test = dd3.nextDouble();
System.out.println(current_test);
System.out.print("Current amount of points in tests: ");
points_test = dd3.nextInt();
System.out.println(points_test);
System.out.print("Amount of points in final: ");
points_final = dd3.nextInt();
System.out.println(points_final);
System.out.print("Desired grade: ");
desired = dd3.nextDouble();
System.out.println(desired);
break;
} catch (Exception e) { // catch non-numerical input
System.out.println(current + "not a double, " + e);
}
dd3.close();
}
}
public static void main(String[] args) { // main method
GradeCalculator calc = new GradeCalculator();
System.out.println("You need a " + String.format("%.2f", calc.calculate()) + " on the test");
}
}
GradeCalculator.main(null);