Ok I've been doing some revision and came across this operator again. I've seen it before but havent fully understood what it does or its surpose to do.

Taken from "Objects first in java 2006"



The example it gives (27 / 4) and the increment function to me dont seem to relate and this is where I'm confused as to why or how modulo is suppose to work. The increment function will increase 'value' by 1 everytime its run untill it reaches an int 'limit' then resets to zero. Well thats how it works but I'm still confused.

For another reason the example is (27 / 4) where as the function would be ((lower number + 1) % limit ). A lower number on the left side % by limit which is a higher number.

/sigh someone help explain this to me so I can figure this out.

This post has been edited by sonesay: Jan 11 2008, 09:31 AM

Modulo is what most people know as "child's division". When you are first taught to divide, you are told to give an answer like "6 remainder 2". Modulo returns the remainder. As far as I can tell, you understand this operation, and what is actually outputted when you use modulo? What you don't understand is how it is being used in the counter.



Lets go for an example. We'll start with value set to 0 and limit set to 7, OK? Good. Below I'll list what the code does and what output you'll get. Perhaps you'll spot the pattern and why it works:

• value = (0+1)%7 = 1%7 1/7 = 0 remainder 1 OUTPUT: 1
• value = (1+1)%7 = 2%7 2/7 = 0 remainder 2 OUTPUT: 2
• value = (2+1)%7 = 3%7 3/7 = 0 remainder 3 OUTPUT: 3
• value = (3+1)%7 = 4%7 4/7 = 0 remainder 4 OUTPUT: 4
• value = (4+1)%7 = 5%7 5/7 = 0 remainder 5 OUTPUT: 5
• value = (5+1)%7 = 6%7 6/7 = 0 remainder 6 OUTPUT: 6
• value = (6+1)%7 = 7%7 7/7 = 1 remainder 0 OUTPUT: 0
• value = (0+1)%7 = 1%7 8/7 = 0 remainder 1 OUTPUT: 1
• Continuing in an infinite loop...

As value is increased each time, the number you are dividing by 7 also increases. As this happens, the remainder you get also increases. When you reach a number that is in the 7 times table, there is no remainder (as it divides exactly by 7) so the counter appears to reset to 0. This also resets 'value' to 0, and the sequence begins again.



The lower number divided by a large number is shown in my example above. The large number goes into the small number 0 times, leaving a remainder equal to the small number.