While loop code output

Question

 int x = 13; 
 while(x >= 4) { 
 if (x % 2 == 1) { 
 System.out.println(x); 
 } 

 x = x - 3; 
 }

I know the output of this, it is 13 and 7, would someone care to explain as how it came to be 13 and 7.

Do you know what % means? It's the modulus operator. To find out what the program does, follow the steps in your head, and write on a piece of paper what happens on each step. — Jesper
– Jesper, Commented Apr 10, 2013 at 6:54
what's wrong with it, it is working fine, first it';; check for 13 and prints it, then for 10, and then for 7 and prints it and then for 4 — Deepanshu Goyal
– Deepanshu Goyal, Commented Apr 10, 2013 at 6:54
Substitute the value 13, 10 and so on for x . Now follow the statements and what it prints in your notebook. — sakthisundar
– sakthisundar, Commented Apr 10, 2013 at 6:55
i believe the % finds the reminder if i am correct. i understand where the 13 comes from but don't quite understand how it gives out a 7. — Philip Hung
– Philip Hung, Commented Apr 10, 2013 at 6:56

OGH · Accepted Answer · 2013-04-10 06:55:08Z

2

13 % 2 = 1 therefore, you print 13. Now x = 10. 10 % 2 = 0, so you dont print out 10. Now x = 7. 7 % 2 = 1, so you print 7. Now x = 4. 4 % 2 = 0; Now x = 1 and the loop stops.

The % operator is the modulo operator. This prints the remainder when dividing two numbers. For example 14/3 = 4 remainder 2, so 13 % 4 = 2.

answered Apr 10, 2013 at 6:55

OGH

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1 Comment

Philip Hung Over a year ago

Ahhhh i see , it was fairly simple, thanks for your answer will accept as soon as i can.

Eugene · Accepted Answer · 2013-04-10 06:54:56Z

2

First x is 13, is it >= then 4? Yes. Enter the while loop. Is 13%2==1. Yes. Print x (print 13). Then x = x-13, x becomes 10. Is 10 >=4? Yes. .... So on.

answered Apr 10, 2013 at 6:54

Eugene

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Comments

BobTheBuilder · Accepted Answer · 2013-04-10 06:55:30Z

2

What don't you understand?

At the first iteration, x=13, 13%2=1 so it prints 13. The seconds iteration, x=10 (x=x-3) 10%2=0, nothing is printed. The third iteration x=7 (10-3), 7%2=1 so 7 is printed.

After that, x=4 so nothing is printed and x=1 quits the loop.

answered Apr 10, 2013 at 6:55

BobTheBuilder

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Comments

Koushik Shetty · Accepted Answer · 2013-04-10 07:16:21Z

2

case 1:

---> x = 13;
     while(true) //  13 >= 4
     if(true)    // 13%2 = 1 which is 1==1  is true
     then print x
     reduce x by 3 // now x ==10

case 2 :

---> x = 10;
     while(true) // 10 > =4
     if(false) // 10 % 2 = 0, 0 == 1 is false
     skip
     reduce x by 3// now x == 7

case 3:

---> x =7;
     while(true) // 7 > = 4
     if(true) //7 % 2 ,1==1 is true
     print x;
     reduce x by 3 // x == 4

case 4:

---> x =4;
     while(true) // 4 > = 4
     if(false) //4 % 2 ,0==1 is false
     skip
     reduce x by 3 // x == 4

case 5:

---> x =1;
     while(false) // 7 > = 4
     skip

operator summary :
**%** finds remainder // result is undefined if RHS operand is 0
**>=** greater than or equals

edited Apr 10, 2013 at 7:16

answered Apr 10, 2013 at 7:01

Koushik Shetty

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