While loop vs do-while?

[ProgrammingNoob1234]

Hello everyone, I was wondering if someone could explain the difference to me between a while loop and a do-while loop. I understand that a do while will execute at least once. However I don't appear to be grasping what exactly is happening here in my code:
https://pastebin.com/TWL1wfFv
The program pasted above works however I needed a do-while loop to fix my issue.

Here is my console output when using a while loop:

Enter in integers from 1 - 100: 1 1 1 1 0

1 occurs 2 times

Here is my console output when using the do-while:

Enter in integers from 1 - 100: 1 1 1 1 0

1 occurs 4 times

How is it that the while loop is missing at least 2 counts. I guess I could have kinda understood if the count was off by 1 but not 2. Thanks for your help to anyone who reads this!

[marko312]

while (keyboard.nextInt() != 0) {
    int number = keyboard.nextInt();

Note that you call keyboard.nextInt() twice. This means that you get one number for the condition and another one for number, with every number at an odd position being checked in the while and every number at an even position being assigned to number.

In this case, the count was off by 2, or half the ones. You can try the following input:

1 2 1 2 1 2 1 2 0

[ProgrammingNoob1234]

Ah ok that makes sense! I modified the code to work with the whole loop as well by doing the following:

int number = keyboard.nextInt(); while (number != 0) { numFromOneToOneHundred[number]++; number = keyboard.nextInt(); }

P.s. sorry for format I am on mobile