someone explain this code (which i mostly understand

public class Program {
    public static void main(String[] main) {
        Scanner scanner = new Scanner (System.in);
        
       
        while (true) {
            
           System.out.println("insert positive integers, 0 to stop");
           int num = Integer.valueOf(scanner.nextLine());
           if(num < 0) {
               System.out.println("thats not a positive integer, try again!");
               continue;
           }
           if (num == 0) {
               
               
               break;
           }
           System.out.println("you put " + num);
           
           
        }
        System.out.println("thanks for adding!");
    }    
} 

public class Program {
    public static void main(String[] main) {
        Scanner scanner = new Scanner (System.in);
        
       
        while (true) {
            
           System.out.println("insert positive integers, 0 to stop");
           int num = Integer.valueOf(scanner.nextLine());
           if(num < 0) {
               System.out.println("thats not a positive integer, try again!");
               continue;
           }
           if (num == 0) {
               
               
               break;
           }
           System.out.println("you put " + num);
           
           
        }
        System.out.println("thanks for adding!");
    }    
} 

public class Tax {

    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("gifts have tax rates depending on their prices, enter your gifts price to calculate the tax rate");
        double tax;
        int price = Integer.valueOf(scanner.nextLine());
        double finalamount;
        
        if (price >= 5000 && price <= 25000) {
            tax = (double) 100 + price * 0.08;
            finalamount = (double) price + tax;
            System.out.println("the gift now costs " + finalamount + " due to a " + tax + " dollar tax");
        }
        else if(price <= 55000) {
            tax = (double) 1700 + price * 0.10;
            finalamount = (double) price + tax;
            System.out.println("the gift now costs " + finalamount + " due to a " + tax + " dollar tax");
        }    
        else if(price <= 200000) {
            tax = (double) 4700 + price * 0.12;
            finalamount = (double) price + tax;
            System.out.println("the gift now costs " + finalamount + " due to a " + tax + " dollar tax");
        }
        else if(price <= 1000000) {
            tax = (double) 22100 + price * 0.15;
            finalamount = (double) price + tax;
            System.out.println("the gift now costs " + finalamount + " due to a " + tax + " dollar tax");
        }
    }
} 

public class Tax {

    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("gifts have tax rates depending on their prices, enter your gifts price to calculate the tax rate");
        double tax;
        int price = Integer.valueOf(scanner.nextLine());
        double finalamount;
        
        if (price >= 5000 && price <= 25000) {
            tax = (double) 100 + price * 0.08;
            finalamount = (double) price + tax;
            System.out.println("the gift now costs " + finalamount + " due to a " + tax + " dollar tax");
        }
        else if(price <= 55000) {
            tax = (double) 1700 + price * 0.10;
            finalamount = (double) price + tax;
            System.out.println("the gift now costs " + finalamount + " due to a " + tax + " dollar tax");
        }    
        else if(price <= 200000) {
            tax = (double) 4700 + price * 0.12;
            finalamount = (double) price + tax;
            System.out.println("the gift now costs " + finalamount + " due to a " + tax + " dollar tax");
        }
        else if(price <= 1000000) {
            tax = (double) 22100 + price * 0.15;
            finalamount = (double) price + tax;
            System.out.println("the gift now costs " + finalamount + " due to a " + tax + " dollar tax");
        }
    }
}