Implementation of congruence in java

Question

Is there a way to calculate if an integer is congruent with the expression 17 modulo 5 in java. The expression could be any variation of the x modulo y. Any ideas on how to make a method to check for this?

Answer 1

You can use Java's remainder operator %. If a and b are both positive, a % b equals the a mod b.

However, the (mathematical) meaning of modulo is a bit different. If b is positive, a % b has the same sign a a. Thus -3 % 10 = -3, while -3 mod 10 = 7. To calculate the modulo, you can use

int result = a % b;
if (result < 0 && b > 0) {
    result += b;
}

or as a single expression:

((a % b) + b) % b

Answer 2

Here it is ;)

% : (Modulus)

Divides left-hand operand by right-hand operand and returns remainder.  

If A=10 and B=20 : B % A will give 0

So a test like : if(a%b==0) will surely help you ;)

Answer 3

If for example you want to make a conditional statement like x an integer :

x = 1[4]

or x congruent to 1 modulo 4

simply write :

if ((x % 4)==1) {
    ...
}

You can apply this in a multitude of other applications.