how does a modulus work when you want to print set of numbers per line

Question

Can someone please explain to me how does the modulus work if you wanna print set of numbers per line like in the given code below? I only know that the role of the modulus is to give the remainder of a number and that's about it. I would like to know the process it goes through.

int []arrayLoterry= new int[50];
String output="";

   for(int i=0;i<arrayLoterry.length;i++){
      arrayLoterry[i]=(int) Math.floor(Math.random()*49)+i;
      output+=arrayLoterry[i]+" ";

      if(i%10==9){
         output+="\n";
      }
   }

System.out.println(output);

Possible duplicate of [How does the modulus operator work?](http://stackoverflow.com/questions/12556946/how-does-the-modulus-operator-work) — MrZander, May 17 '17 at 00:23
refer this [post](http://stackoverflow.com/questions/4403542/how-does-java-do-modulus-calculations-with-negative-numbers) it may be helpful. — Rajith Pemabandu, May 17 '17 at 00:24
There is no modulus operator in Java. This is the [remainder operator](http://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.17.3). — user207421, May 17 '17 at 00:41

Ousmane D. · Answer 1 · 2017-05-17T02:35:15.127

The if condition simply checks if the remainder of i % 10 is 9 then performs the task within the if block. In regards to your code, basically, after every 10 numbers appended to the string output, a newline will be appended to the string output in order to separate the lines.

Example:

when i == 9 // append newline
when i == 19 // append newline
when i == 29 // append newline
when i == 39 // append newline
when i == 49 // append newline

meaning the end result will be a 5 x 10 matrix.

side note - I wouldn't recommend concatenating strings within a loop as that is a performance bottleneck, you're better off using a StringBuilder along with StringBuilder#append method.

score 1 · Accepted Answer · 2017-05-18T01:31:53.683

1

This statement:

if(i%10==9){
    output+="\n";
}

Is saying: "If i divided by 10 leaves the remainder of 9, add "\n"(which is a new line) to variable output.

Moduli simply divide the first number by the second, and give the remainder. Examples below:

10%3 = 1  
20%2 = 0  
7%4 = 3

In your case, this will start a new lie after every 10 numbers. You might think, Why not change that statement to if(i%10 == 0)? The reason it is i%10 == 9 is because when the loop executes the first time, i holds the value of 0, so when it runs through the modulus, the answer is 0, which makes a new line after the first execution of the loop.

Since Java counts 0, 1, 2 like we count 1, 2, 3, we have to make the line break after everything that ends in 9. So a new line starts after the 9th(10th for us), 19th(20th for us), 29th(30th), 39th(40th), and 49th(50th and last) number outputted.

This chart shows how Java counts, versus how we count.

Java | 0 1 2 3 4 5 6 7 8 9 
----------------------------
Us!! | 1 2 3 4 5 6 7 8 9 10

edited May 18 '17 at 01:31

answered May 17 '17 at 00:23

@BlueEagle - [this wikipedia article](https://en.wikipedia.org/wiki/Modulo_operation) might help you to understand. – May 17 '17 at 00:50
its a bit clear. But since if the answer of the remainder is 0 prints a new line, how come it doesn't print after the first number when we have (i%7==3) in the if? – Blue Eagle May 17 '17 at 01:45
When the answer is 0, it does not print a new line. it prints a new line when the remainder is 9 – May 17 '17 at 02:01
I think your getting confused, there is no `(i%7==3)`, when the loop runs. the variable `i` refers to how many times the loop runs. The modulo gets the remainder of i/10 and if that = 9, it prints a new line. This will print a new line after every 10 numbers. – May 17 '17 at 02:31
@BlueEagle to simplify, that `if` statement simply prints a new line after every ten numbers outputted. If this answer was the most helpful, please accept it :) – May 18 '17 at 01:27

how does a modulus work when you want to print set of numbers per line

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