Java tutorial 1

App.java

package selection;

import java.util.Scanner;

public class App {


    /**
     * Bonus rating from 1 to 3. Each rating provides a percentage bonus
     * amount based on their pay.
     * 1: 5%
     * 2: 10%
     * 3: 15%
     */

    /**
     * We declare these as constants using the "final" keyword since we don't need to change or "mutate" them. 
     * This lets the Java know exactly how much memory to allocate.
     * 
     * We also declare them outside of the main() function, this means any
     * other methods in this class can see and read them. We don't have any other methods yet, but we might add some later.
     * These are called "class variables".
     */
    static final String EMPLOYEE_NAME = "George";
    static final double EMPLOYEE_SALARY  = 25000.00d;

    /**
     * It would take me ages to explain this properly. I'm sure we'll go over it anyway.
     * Basically, this defines this class' main function. Which means, when the code is compiled,
     * this is always run. 
     * 'void' tells the compiler that the method does not "return" anything. It doesn't produce anything, it just 
     * prints to the console. 
     * We pass in String[] args as an argument. This isn't important for now. Just know it means an array of Strings, called "args". 
     */
    public static void main( String[] args ) {
        
        /**
         * We create a new instance of the Scanner object. You can read more
         * about it here:
         * https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html
         * 
         * It's actually a little complicated. The scanner basically just takes what you type in (System.in) 
         * word-by-word, and reads them as any data type we want.
         */
        Scanner stdin = new Scanner(System.in);

        System.out.println("Enter your employee bonus rating: ");

        // Tells the scanner to read the next thing we type into our terminal (System.in) as an integer. 
        // It will try to do this even if you type in words, or a binary number, or even a file. So be careful! 
        int bonusRating = stdin.nextInt();

        /**
         * We declare the variable first, before modifying the value in the If statements.
         * If we were to create variables within the If/Else/Elseif blocks, 
         * They would only exist within those blocks, and would then be destroyed when the blocks have finished executing..
         * We need to use totalSalaryWithBonus later, so we need them to stay in memory.
        */
        double totalSalaryWithBonus;

        /**
         * We are comparing what the user typed in (stored in bonusRating variable) 
         * to 1 and 2 to see if they are equal. And in any other case (maybe they type in 1000, or 0) we can just assume
         * they meant to say 3. :D
         * When you learn a bit more Java, you can raise errors if the user types something in wrong, or try asking for input again.
         */
        if (bonusRating == 1) {
            totalSalaryWithBonus = EMPLOYEE_SALARY * 1.05;
        }
        else if (bonusRating == 2) {
            totalSalaryWithBonus = EMPLOYEE_SALARY * 1.10;
        }
        else {
            totalSalaryWithBonus = EMPLOYEE_SALARY * 1.15;
        }

        /**
         * Output should look like this:
         * 
         * Employee Name: George
         * Employee Salary: 25000.00
         * Employee Salary with Bonus: 26250.00
         */
        System.out.printf("Employee Name: %s\nEmployee Salary: %.2f\nEmployee Salary with Bonus: %.2f", EMPLOYEE_NAME, EMPLOYEE_SALARY, totalSalaryWithBonus);
        
        /**
         * It's generally good practice to close any object in code which reads from files or user input,
         * for the sake of security but also efficient memory usage. This deletes the Scanner object from memory, if we try referring to it again after closing it, 
         * we will get an error.
         * In this case, it doesnt matter, since this is the last line of code and the program terminates afterwards anyway :P 
         */
        stdin.close();

        
    }
}