Java - How to get next or previous item from a Collection?

Java Collections Java 

Following example shows how to get next or previous item from a java.util.Collection. The flag 'circular' allows to cycle the collection indefinitely.

package com.logicbig.example;

import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;

public class CollectionNextPrevItem {

    public static <T> T getNext(Collection<T> collection, T target) {
        return getNext(collection, target, false);
    }

    public static <T> T getNext(Collection<T> collection, T target, final boolean circular) {
        if (collection == null) {
            return null;
        }
        Iterator<T> itr = collection.iterator();
        T first = null;
        boolean firstItr = true;
        while (itr.hasNext()) {
            T t = itr.next();
            if (circular && firstItr) {
                first = t;
                firstItr = false;
            }
            if (Objects.equals(t, target)) {
                return itr.hasNext() ? itr.next() : circular ? first : null;
            }
        }
        return null;
    }

    public static <T> T getPrevious(Collection<T> collection, T target) {
        return getPrevious(collection, target, false);
    }

    public static <T> T getPrevious(Collection<T> collection, T target, final boolean circular) {
        if (collection == null) {
            return null;
        }
        Iterator<T> itr = collection.iterator();
        T previous = null;
        boolean firstItr = true;
        while (itr.hasNext()) {
            T t = itr.next();
            if (Objects.equals(t, target)) {
                if (firstItr && circular) {
                    for (; itr.hasNext(); t = itr.next())
                        ;
                    return t;
                } else {
                    return previous;
                }
            }
            previous = t;
            firstItr = false;
        }
        return null;
    }


    public static void main(String[] args) {
        List<String> list = List.of("one", "two", "three", "four");
        String s = getNext(list, "three");
        System.out.println(s);
        s = getPrevious(list, "three");
        System.out.println(s);
        s = getNext(list, "four");
        System.out.println(s);
        s = getPrevious(list, "one");
        System.out.println(s);

        System.out.println("-- circular --");
        s = getNext(list, "four", true);
        System.out.println(s);
        s = getPrevious(list, "one", true);
        System.out.println(s);
    }
}

four
two
null
null
-- circular --
one
four