可被5或6整除

Question

I am trying to make a program where it lists all the numbers between 100-1000 that are divisible by 5 or 6. This is the code I used:

public class divisibleBy5and6 {
    public static void main (String[] args) {

        j = 1; 
        int number = 100;
        while (number < 1001) {
            if (number % 6 == 0 || number % 5 == 0) {
                System.out.print(number + ", ");
                number++;
                j++; }

            if (j % 10 == 0 && j != 0) {
                System.out.println();
                j++; }
            else {
                number++;
            }
        }

I used int j to make it so there are 9 per row. This is my output:

100, 102, 105, 108, 110, 114, 120, 125, 130, 
132, 135, 138, 140, 144, 150, 155, 160, 162, 
165, 168, 170, 174, 180, 185, 190, 192, 195, 
198, 200, 204, 210, 215, 220, 222, 225, 228, 
230, 234, 240, 245, 250, 252, 255, 258, 260, 
264, 270, 275, 280, 282, 285, 288, 290, 294, 
295, 300, 305, 310, 312, 315, 318, 320, 324, 
325, 330, 335, 340, 342, 345, 348, 350, 354, 
355, 360, 365, 370, 372, 375, 378, 380, 384, 
385, 390, 395, 400, 402, 405, 408, 410, 414, 
415, 420, 425, 430, 432, 435, 438, 440, 444, 
445, 450, 455, 460, 462, 465, 468, 470, 474, 
475, 480, 485, 490, 492, 495, 498, 500, 504, 
505, 510, 515, 520, 522, 525, 528, 530, 534, 
535, 540, 545, 550, 552, 555, 558, 560, 564, 
565, 570, 575, 580, 582, 585, 588, 590, 594, 
595, 600, 605, 610, 612, 615, 618, 620, 624, 
625, 630, 635, 640, 642, 645, 648, 650, 654, 
655, 660, 665, 670, 672, 675, 678, 680, 684, 
685, 690, 695, 700, 702, 705, 708, 710, 714, 
715, 720, 725, 730, 732, 735, 738, 740, 744, 
745, 750, 755, 760, 762, 765, 768, 770, 774, 
775, 780, 785, 790, 792, 795, 798, 800, 804, 
805, 810, 815, 820, 822, 825, 828, 830, 834, 
835, 840, 845, 850, 852, 855, 858, 860, 864, 
865, 870, 875, 880, 882, 885, 888, 890, 894, 
895, 900, 905, 910, 912, 915, 918, 920, 924, 
925, 930, 935, 940, 942, 945, 948, 950, 954, 
955, 960, 965, 970, 972, 975, 978, 980, 984, 
985, 990, 995, 1000, 

This obviously isn't right because I am missing numbers like 115 . What am I doing wrong?

Answer 1

You need to seperate the number incrementation from the if/else statements. It should happen at each iteration no matter what...

int j = 1; 
int number = 100;
while (number < 1001) {
  if (number % 6 == 0 || number % 5 == 0) {
    System.out.print(number + ", ");
    j++; 
   }
   if (j % 10 == 0) {
     System.out.println();
   }
   number++;
}

Answer 2

The problem is that sometimes, you're incrementing number twice in each loop. The first time is if the number is a multiple of 6 or of 5 , and the second time is when you don't print a newline. This has the effect of skipping numbers, such that consecutive multiples of 5 or 6 won't print, such as your 115 , because it's after 114 and is skipped. Notice also that other consecutive multiples of 5 or 6 won't print, such as the 126 after the 125 .

Make it clear that you increment number only once per loop but removing number++; from the if and else blocks, and unconditionally increment by placing number++; at the very bottom of the while loop.

Answer 3

remove the first place it says number++; after the System.out.print(number + ", ");

alter

else {
                number++;
            }

It does this when you've just printed a newline.

to

            number++;

It will do this on every loop iteration number should be incremented non conditionally

Answer 4

Try this:

public class DivisibleBy5and6 {
    public static void main (String[] args) {

        int j = 1; 
        for (int number = 100 ; number < 1001; number++) {
            if (number % 6 == 0 || number % 5 == 0) {
                System.out.print(number + ", ");
                j++; 
            }

            if (j % 10 == 0) {// j never equals 0
                System.out.println();
                j++; 
            }
        }
    }
}

BTW, For definite loops it's better to use for instead of while . (makes your code more readable)

As you see you don't get confused this way and increase number once and in the right place.

Answer 5

You had a duplicate number++ which was executed twice when both conditions were true. That overjumps some values: now corrected:

int j = 1;
int number = 100;
while (number < 1001) {
    if (number % 6 == 0 || number % 5 == 0) {
        System.out.print(number + ", ");
        j++;
    }

    if (j % 10 == 0 && j != 0) {
        System.out.println();
        j++;
    }
    number++;
}

Answer 6

Your problem is that the code is incorrectly formatted. Properly indent it and it becomes much clearer:

public class divisibleBy5and6 {
    public static void main (String[] args) {

        j = 1; 
        int number = 100;
        while (number < 1001) {
            if (number % 6 == 0 || number % 5 == 0) {
                System.out.print(number + ", ");
                number++;
                j++;
            }

            if (j % 10 == 0 && j != 0) {
                System.out.println();
                j++;
            }
            else {
                number++;
            }
        }

Then you can see that the else is attached to the second if , not the first, so the incrementing of number can occur twice.

After that it's clearer that, inside the first if , number is incremented ONLY if the number is printed. What you really want is for number to be incremented for every iteration, and the best way to assure that is to ONLY increment number immediately prior to the closing } of the while .

Then you'll realize that the while(number < 1001) ... number++ loop can be replaced with a more robust for (int number 100; number < 1001; number++) , totally removing the incrementing of number from the loop body.

When designing a loop it's quite important to keep straight which values are "invariant" in the loop (never change at all), which are simply incremented with each iteration, and which are modified on a more irregular basis. If you keep these concepts straight then loops are much less intimidating.

Answer 7

public class pattern {
    public static void main (String[] args) {

        int j = 0; 
        int number = 100;
        while (number < 1001) {
            if (number % 6 == 0 || number % 5 == 0) {
                System.out.print(number + ", ");
                j++; }

            if (j % 10 == 0&&(number % 6 == 0 || number % 5 == 0)) {
                System.out.println();
                number++;     
            }
            else
            {
                number++;
            }
        }
    }
}

Try this code.

The mistake in your code is that you are actually incrementing number twice so that's why you are missing some numbers. Good luck :)