In this post, we feature a comprehensive article about Java Modulus operator, modulo otherwise. We are going to learn what does ‘%’ mean in Java.
1. Introduction
This article will show the usage of the modulo operation in Java that computes the remainder after the division of 2 numbers. Java uses a specific arithmetic operator the Remainder Operator with the symbol %.
2. Java Modulus – Use Cases
In this section we show same useful use cases .
2.1 Basic Usage
Create a class with name ModulusExample1 and paste the following code :
ModulusExample1.java
package com.javacodegeeks;
/**
* @author Petros Koulianos
*
*/
public class ModulusExample1 {
public static void main(String[] args) {
int x = 3;
int z = 10;
int y = -23;
int w = -12;
double d = 2.15;
float f= 3.6f;
int zero=0;
//positive number modulus positive number
//the result is the remainder of the division
System.out.println("positive number modulus positive int number: "+z % x);
System.out.println("positive number modulus positive double number: "+z % d);
System.out.println("positive number modulus positive float number: "+z % f);
//negative number modulus positive number
//the result is negative
System.out.println("negative number modulus positive number: "+ y % z);
//negative number modulus negative number
//the result is the negative remainder of the division
System.out.println("negative number modulus negative number: "+w % y);
//zero number modulus number
//the result is zero
System.out.println("zero modulus number : "+zero % z);
// number modulus zero
//throws java.lang.ArithmeticException , it must surround with try catch brackets
//in order to avoid crush the execution
try {
System.out.println("number modulus zero : "+z % zero);
}catch(ArithmeticException e) {
//print stack trace
e.printStackTrace();
}
}
}
Console Output
positive number modulus positive int number: 1 positive number modulus positive double number: 1.4000000000000004 positive number modulus positive float number: 2.8000002 negative number modulus positive number: -3 negative number modulus negative number: -12 zero modulus number : 0 java.lang.ArithmeticException: / by zero at com.javacodegeeks.ModulusExample1.main(ModulusExample1.java:48)
2.2 Find if a number is odd or even
Create a class with name ModulusExample2 and paste the following code :
ModulusExample2.java
package com.javacodegeeks;
/**
* @author Petros Koulianos
*
*/
public class ModulusExample2 {
public static void main(String[] args) {
// find out when a number is even or odd
for(int i=0 ; i<=10000; i++) {
//modulus each number with 2
if(i % 2 == 0) {
//number is even
System.out.println("number "+i+" is even");
}else {
//number is odd
System.out.println("number "+i+" is odd");
}
}
}
}
The most noteworthy case to use the modulo operation is to find if a given number is even or odd . The above code run a loop to check the numbers if it is odd or even , by modulus each number by 2.
2.3 Perform an action at nth number of times in loop
Create a class with name ModulusExample3 and paste the following code :
ModulusExample3.java
package com.javacodegeeks;
import java.util.ArrayList;
import java.util.List;
/**
* @author Petros Koulianos
*
*/
public class ModulusExample3 {
public static void main(String[] args) {
// perform an action at n-th number of loops
List bigList = getList();
int n = 1000; // n-th times
for (int i = 0; i < bigList.size(); i++) {
// check the process of the running list every 1000 loops
if (i % n == 0) {
// calculate the process of the running list
double process = (100 * i) / bigList.size();
// you can update your UI with a process bar
System.out.println("process " + process + "%");
}
}
// your list ended
System.out.println("process 100.0%");
}
// method to generate a list, simulating a very large dataset
// from database or file(csv , xml etc) or web service (json etc)
public static List getList() {
List list = new ArrayList();
for (int i = 0; i < 98562; i++) {
double x = Math.random();
list.add(x * 1000);
}
return list;
}
}
Console Output
process 0.0% process 1.0% process 2.0% ... ... ... process 98.0% process 99.0% process 100.0%
2.4 Find the greatest common divisor
The euclidian algorithm uses the modulo operation , in order to find the greatest common division.
Create a class with name ModulusExample4 and paste the following code :
ModulusExample4.java
package com.javacodegeeks;
/**
* @author Petros Koulianos
*
*/
public class ModulusExample4 {
public static void main(String[] args) {
// This example implements the Euclidean algorithm from
//https://en.wikipedia.org/wiki/Euclidean_algorithm#Implementations
int a = 1071;
int b = 462;
int temp ;
while (b != 0) {
temp = b;
b = a % b;
a = temp;
}
System.out.println("The Greatest Common Division is "+a);
}
}
Console Output
The Greatest Common Division is 21
2.5 Find out if an integer is prime number.
Another usage of modulo operation is in the algorithm of prime numbers .
Create a class with name ModulusExample5 and paste the following code :
ModulusExample5.java
package com.javacodegeeks;
/**
* @author Petros Koulianos
*
*/
public class ModulusExample5 {
public static void main(String[] args) {
//This example implements prime number algorithm
//from https://en.wikipedia.org/wiki/Prime_number#Computational_methods
int x = 28 ;
int y = 113;
int temp1 = 0;
int temp2 = 0;
// run a loop from 2 to square root x
for(int i=2 ; i <= Math.sqrt(x); i++) {
if(x % i == 0) {
// i number can multiply x
temp1 ++;
}
}
// run a loop from 2 to square root y
for(int i=2 ; i <= Math.sqrt(y); i++) {
if(y % i == 0) {
// i number can multiply y
temp2 ++;
}
}
// if x or y has zero multipliers is prime
if(temp1 == 0) {
System.out.println("number "+x+" is prime");
}else {
System.out.println("number "+x+" is not prime");
}
if(temp2 == 0) {
System.out.println("number "+y+" is prime");
}else {
System.out.println("number "+y+" is not prime");
}
}
}
Console Output
number 28 is not prime number 113 is prime
3. Download the Source Code
This was an example about how to use the Java Modulus ( Remainder Operator ).
You can download the full source code of this example here: Java Modulus Example
