Java Primitives

• What I learned
  • Useful stuff learned while creating calculator:
  • Playing with Code from Primitive Data Types
  • Variables
  • Input + Output

public class AvgCalculator{
    public static void main(String[] args) {
        // numDouble: User's input is a string, will be changed into a double
        // Double is used to allow user to input decimal numbers
        double numDouble = 0;
        double sum = 0;
        // count = n (sample size to determine mean)
        // Sample size is always a whole number (ex: 1, 2, etc.)
        int count = 0;
        double mean = 0;

        Scanner sc = new Scanner(System.in);
        System.out.println("Enter numbers, type 'end' to finish");

        while (true) {
            // String is used as the input for each number
            // The reason why I didn't use int was because I wanted the user to 
            // be able to end the calculator by typing "end"
            System.out.println("Number: ");
            String numStr = sc.next(); 
            System.out.println(numStr);
            if ("end".equals(numStr)) {
                break;
            }
            
            // This performs casting by changing the input, which was a string,
            // into a double so that the mean can by determined
            numDouble = Double.parseDouble(numStr);  
            sum += numDouble;
            count++;  
            
        }
        
        mean = sum/count;

        System.out.println("Show detailed info? y/n");
        String detail = sc.next();
        // Setting showDetail as true/false, this can be used in the future
        // as a toggle. (If showDetail = true, show more detail, otherwise,
        // only show the result)
        // Also showDetail can only be yes/no, so it can be set as a boolean

        System.out.println(detail);

        boolean showDetail;
        if ("y".equals(detail)) {
            showDetail = true;
        } else {
            showDetail = false;
        }

        if (showDetail) {
            System.out.println("Sum: " + sum);
            System.out.println("Count: " + count);
        }
        System.out.println("Mean: " + mean);

    }
    
}
AvgCalculator.main(null)

Enter numbers, type 'end' to finish
Number: 
1
Number: 
2
Number: 
3
Number: 
4
Number: 
5
Number: 
end
Show detailed info? y/n
y
Sum: 15.0
Count: 5
Mean: 3.0

What I learned

Primitives include: int, double, boolean

String is not a primitive.

Code: Integer: int a

Double: double a

Boolean: boolean a

String: String a

To enable input, make sure to import the Scanner lirbary: import java.util.Scanner;

Useful stuff learned while creating calculator:

if and while statements:

If the variable is an integer/double, you can use ==

If the variable is a string, you must use .equals

Example: "foo".equals(variableName)

Playing with Code from Primitive Data Types

Variables

public class test {
    public static void main(String[] args) {
        int x = 5;
        System.out.println("This is an integer: " + x);
    }
}
test.main(null)

This is an integer: 5

Input + Output

import java.util.Scanner;

public class Scanning {
    public static void main(String[] args) {
        Scanner test = new Scanner(System.in);

        System.out.println("Enter a number: ");
        int input = test.nextInt();
        System.out.println(input);
        System.out.println("Your number is: " + input);
    }
}
Scanning.main(null);

Enter a number: 
3
Your number is: 3