line math operation not clear

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i did all the code all by my own exept for the condition of the while in my head was input %10 ==0 , and he line 29, that i find out here in the community but really i can't get what is it. if someone could explain to me why the while loop is (n>0) and line 29 will be great

Use the keyboard to enter a positive number. Determine the number of even digits and odd digits in the entered number.
If a number is divisible by 2 without a remainder (i.e. the remainder is zero), then it is even.
And we'll increase the even digit counter (static variable even) by 1.
Otherwise, the number is odd, so we'll increase the odd digit counter (static variable odd).
Display the following message: "Even: a Odd: b", where a is the number of even digits and b is the number of odd digits.

Example for 4445:
Even: 3 Odd: 1

Requisiti:

The program must read data from the keyboard.
The main method should calculate how many even digits are in the entered number and then write this number to the variable even.
The main method should calculate how many odd digits are in the entered number and then write this number to the variable odd.
The program should display text on the screen.
The displayed text must match the task conditions.

package com.codegym.task.task06.task0606; import java.io.*; import java.util.*; /* Even and odd digits */ public class Solution { public static int even; public static int odd; public static void main(String[] args) throws IOException { //write your code here Scanner s = new Scanner(System.in); int n = s.nextInt(); int i =0; while (n> 0){ i = n % 10; if (i % 2 ==0){ even++; } else if (i % 2 != 0) { odd++; } n /= 10; } System.out.println("Even: " + even + " Odd: " + odd); } }

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Thomas

Livello 41 , Bayreuth, Germany

17 ottobre 2022, 08:00

soluzione

A condition i % 10 == 0 won't work if you consider i to be eg. 100. Then your loop will stop What you want to do: you want to evaluate each digit of a positive number if it is even or odd That sounds easy but is a tough nut to crack. And you're on the best way to the solution So how to proceed: 1. Each digit you get with a loop. As long as there are digits you loop (very simplified). 2. How to get a digit from the number. Yes, that's now modulus (number % 10). It'll give the remainder of the division by 10. Exactly what you want. 3. The problem is, the number didn't change yet. It has still the same number of digits (and the same value) as before. So you need to get rid of the last. Just divide the number by 10 and assign the result to number again (it's a int division, so the decimal places are cut off. Eg. 123 / 10 in double is 12.3 -> in an int division the decimal places get cut off and as a result you have 12). Exactly what we want.

int number = 1234;
// as long as the number has digits
while (number > 0) {
    // get the last digit
    System.out.format("last digit: %d%n", number % 10);
    // remove the last digit
    number = number / 10; // short form: number /= 10;
}

EvelynSt

Livello 10 , Italy

17 ottobre 2022, 08:05

Wow i complete skip one part of the thinking!. Still proud of me what i reach but i forgot to reasign value! Ans we need n>0 so it evaluate every number isn't better >=? What if users add 0?

Thomas

Livello 41 , Bayreuth, Germany

17 ottobre 2022, 08:16

utile

Task conditions: enter a positive number. If you make the condition number >= 0 you'll have an endless loop as 0 / 0 is 0, That's not an abort condition anymore. You also could convert the number to a string and loop over the string... or a char array. A good loop exercise btw ;)

// you also could convert the number to a string
int number = 1234;
String strNum = String.valueOf(number); // "1234"
// loop over the String, convert it to a char array or whatever
for (int i = 0; i < strNum.length(); i++) {
    // from the beginning
    int startDigit = strNum.charAt(i) - '0';
    System.out.format("from start: %d%n", startDigit);
    // from the end
    int endDigit = strNum.charAt(strNum.length() - i - 1) - '0';
    System.out.format("from end: %d%n", endDigit);
}

// char array
for (char c : strNum.toCharArray())
    System.out.println(c);

EvelynSt

Livello 10 , Italy

17 ottobre 2022, 10:45

thanks i will try, what is %d%n" thank you in advice

Thomas

Livello 41 , Bayreuth, Germany

17 ottobre 2022, 16:18

utile

you can format output that way easily

double money = 12.3456;
String name = "Jill";
int age = 26;
Date birthdate = new Date(1996 - 1900, Calendar.FEBRUARY, 15);

String formattedOutput = String.format("""
                %-10s has only $%.2f. Her year of birth is %TY and she is %d years old.
                In hex this is %x.
                """
                ,name, money, birthdate, age, age);

System.out.println(formattedOutput);
/*
Jill       has only $12,35. Her year of birth is 1996 and she is 26 years old.
In hex this is 1a.
*/

%d is a placeholder for a integer, long, short. %n is a linebreak %s a placeholder for String. %10s means the String should use 10 chars. If the String is smaller it gets filled up with spaces. %-10s align the String left. %f double, float. %.2f only print two decimal places. You can format a lot of stuff. Dates, time int to hex... and that all localized Don't look at unknown things you see to closely. I use features like format cause it is convenient for me to type it that way instead of using concatenation. More important is the way of how you split a number into pieces or how you can use loops. Especially the way of reversing the direction is a often used technique. Memorize it.