LEAP-YEAR CALCULATOR

Calculator.java

package demo;

public interface Calculator {
    boolean calculateLeapYear(int year);
}

LeapYear.java

package demo;

public class LeapYear implements Calculator {

    private static final int MULTIPLE = 4;
    private static final int SECULAR = 100;
    private static final int NOT_SECULAR = 400;
    private static final int REMAINDER = 0;


    public boolean calculateLeapYear(int year) {
        return isMultiple(year) && (!isSecular(year) || isNotSecular(year));
    }

    private boolean isMultiple(int year){
        int result = year / MULTIPLE;
        return year == (MULTIPLE * result) ? true : false;
    }

    private boolean isSecular(int year) {
        return year % SECULAR == REMAINDER;
    }

    private boolean isNotSecular(int year) {
        return year % NOT_SECULAR == REMAINDER;
    }

}

LeapYearCalculatorDemo.java

package demo;

public class LeapYearCalculatorDemo {

    private static final int LEAP_YEAR = 2400;

    public static void main(String[]args){
        final Calculator date = new LeapYear();
        System.out.println(date.calculateLeapYear(LEAP_YEAR) ? showLeapYear() : showNotLeapYear());
    }

    private static String showLeapYear(){
        return "Is leap-year";
    }

    private static String showNotLeapYear(){
        return "Is not leap-year!!!";
    }

LeapYearTest.java

#TEST
import demo.Calculator;
import demo.LeapYear;
import org.junit.Test;

import static org.junit.Assert.assertTrue;

public class LeapYearTest {
    private static final int LEAP_YEAR = 2000;
    @Test
    public void isMultipleValidateValue(){
        Calculator calculator = new LeapYear();
        assertTrue(calculator.calculateLeapYear(LEAP_YEAR));
    }
}