Need help understanding this basic challenge?

Currently doing a challenge called number to words, I have created 2 methods, one which
deals with comparing values individually so that it can print out it's string value(method called numberToWord), another method called reverse which basically re-orders the values so that it is printed in a correct sequence, for example:s
Step One 567 --> Step 2, it will be converted into 765 --> Step 3, reverse method will then convert it back to 5,6,7 individually so that it can compare the values with the if statements. However, i have tried so many things to getting this to work, i managed to make it to step 3 but when i try to return the value it gives me 3 random values before it converts e.g = 7,6,7...5,6,7, i am unable to figure out how to remove the first 3 values and return just the last three values so that it can be compared in the numberToWords method.

package com.company;
public class Main {
public static void main(String[] args) {
numberToWords(567);
}
public static void numberToWords(int number) {
int lastDigit = 0;
int digit = number;
int reverseDigit = 0;
if (number < 0) {
System.out.println("Invalid Value");
}
for (int i = 0; i < digit; i++) {
//so we are taking the last digit from 567 per iteration
lastDigit = digit % 10;
//we are then dividing the digit by 10 each time so we can get another last digit
digit /= 10;
//i will now try to essentially get down to the final number which will be flipped
reverseDigit = (reverseDigit * 10) + lastDigit;
//checking values
System.out.println(reverse(reverseDigit));
//            if (reverse(reverseDigit)== 0) {
//                System.out.println("Zero");
//            } else if (reverse(reverseDigit) == 1) {
//                System.out.println("One");
//            }else if (reverse(reverseDigit) == 2) {
//                System.out.println("Two");
//            }else if (reverse(reverseDigit) == 3) {
//                System.out.println("Three");
//            }else if (reverse(reverseDigit) == 4) {
//                System.out.println("Four");
//            }else if (reverse(reverseDigit) == 5) {
//                System.out.println("Five");
//            }else if (reverse(reverseDigit) == 6) {
//                System.out.println("Six");
//            }else if (reverse(reverseDigit) == 7) {
//                System.out.println("Seven");
//            }else if (reverse(reverseDigit) == 8) {
//                System.out.println("Eight");
//            }else if (reverse(reverseDigit) == 9) {
//                System.out.println("Nine ");
//            }
if (lastDigit == 0) {
System.out.println("Zero");
} else if (lastDigit == 1) {
System.out.println("One");
} else if (lastDigit == 2) {
System.out.println("Two");
} else if (lastDigit == 3) {
System.out.println("Three");
} else if (lastDigit == 4) {
System.out.println("Four");
} else if (lastDigit == 5) {
System.out.println("Five");
} else if (lastDigit == 6) {
System.out.println("Six");
} else if (lastDigit == 7) {
System.out.println("Seven");
} else if (lastDigit == 8) {
System.out.println("Eight");
} else if (lastDigit == 9) {
System.out.println("Nine");
}
}
}
public static int reverse (int a){
int lastDigit = 0;
for (int i =0; i < a; i++) {
lastDigit = a % 10;
a /= 10;
//testing values here
//System.out.println(lastDigit);
//sout in loop gives us 567
}
return lastDigit;
}
}

I think you have the right idea of doing remainder division for numberToWords() and reverse().
But I think you're condition for exiting the for loop is wrong

for (int i = 0; i < digit; i++)

It will exit before you get all the digits. You want to loop until digit is 0, since you want to remainder divide UNTIL there's no more to divide ( meaning digit is 0).

so

for(int i = 0; digit != 0; i++){
...
}

while loop might be better than a for a loop since you're not using i anyways.

while(digit != 0){
...
}

It also depends on which IDE you're using but IntelliJ and eclipse can do a line by line debug so you see which line is causing issues.

If I understand what you need correctly, you don't need that much code. Just print the reminder of division by 10 and then divide by ten for then next iteration until you get zero.

enum Numbers {
Zero,
One,
Two,
Three,
Four,
Five,
Six,
Seven,
Eight,
Nine;
}
private static void process(int number) {
do {
final int digit = number % 10;
System.out.println(Numbers.values()[digit]);
number /= 10;
} while (number > 0);
}

First use an enum since you can use it like an array but easier to declare. Then with the number you get, first get the reminder over ten. For any integer expressed as decimal the reminder over ten is the last digit. Since you have to print the last digit in the first place, just print it. Then replace number with number divided by ten. That will discard the last digit (the one just printed out) because this is an integer division. I mean, 1234 over 10 is 123.4 but because these are integer it gets truncated to 123. So now loop and the last digit will be printed again (but now it will be the first to the left due to the division). At some point, after printing the first digit of the original number you will have a one digit integer (i.e. 7) divided by ten which results in zero (because it would be 0.7 but it's an integer division).
You need to add some preconditions like the negatives.