So apparently there's a library for that...

LeapYear.java

package uk.ac.qub.programming;

import java.util.GregorianCalendar;

public class PartThree9 {

    public static void main(String[] args) {

        GregorianCalendar calendar = (GregorianCalendar) 
                GregorianCalendar.getInstance();
        
        for (int counter = 1800; counter < 2013; counter++) {
            boolean isLeapYear = calendar.isLeapYear(counter);
            if (isLeapYear) {
                System.out.println(counter);
            } else {
                continue;
            }
        }
    }
}