How to get the nth previous or next element in Jsoup

Question

Is there is anyway to get the nth previous or next specific HTML element that could possibly be on a different nesting level using jsoup?

HTML example:

 <div style="position: relative;"> <div class="wmd-container"> <div id="wmd-button-bar-42" class="wmd-button-bar"></div> <input id="previousInput" name="communitymode" type="checkbox"> </div> </div> <div class="fl" style="margin-top: 8px; height: 24px;">&nbsp;</div> <div id="draft-saved-42" class="draft-saved community-option fl" style="margin-top: 8px; height: 24px; display: none;">draft saved </div> <div id="draft-discarded-42">draft discarded</div> <div class="community-option g-row ai-center f-checkbox"> <div class="g-col -input"> <input id="NextInput" name="communitymode"> </div> <div class="g-col"> <label for="communitymode-42">community wiki</label> </div> </div> 

For example in below HTML I am pointing the element:

 <div id="draft-discarded-42">draft discarded</div> 

by using below code.

Element elem = doc.select("div[id=draft-discarded-42]").first();

I want the first previous input element:

 <input id="previousInput" name="communitymode" type="checkbox"> 

And the second previous div :

 <div class="fl" style="margin-top: 8px; height: 24px;">&nbsp;</div> 

And the second next div :

 <div class="g-col -input"> <input id="NextInput" name="communitymode"> </div> 

Answer 1

Unless you don't know the id attribute's value or any attribute that you can use to identify an element , you should use the selector syntax to get the element you want.

However, if you have a vague idea/don't know about the element's attributes, but know its occurrence relating to the pointed element, you can use these functions:

Nth previous occurrence of an element matching the query:

public static Element selectNthElementBefore(Element origin, String query, int count) {
    Element currentElement = origin;
    Evaluator evaluator = QueryParser.parse(query);
    while ((currentElement = currentElement.previousElementSibling()) != null) {
        int val = 0;
        if (currentElement.is(evaluator)) {
            if (--count == 0) {
                return currentElement;
            }
            val++;
        }
        Elements elems = currentElement.select(query);
        if (elems.size() > val) {
            int childCount = elems.size() - val;
            int diff = count - childCount;

            if (diff == 0) {
                Element prevElement = elems.first();
                currentElement = prevElement.children().select(query).first();
                while (currentElement != prevElement) {
                    if (currentElement == null) {
                        return prevElement;
                    }
                    prevElement = currentElement;
                    currentElement = currentElement.children().select(query).first();
                }
            }
            if (diff > 0) {
                count -= childCount;
            }
            if (diff < 0) {
                return elems.get(childCount - count);
            }
        }
    }

    if (origin.parent() != null && currentElement == null) {
        if (origin.parent().is(evaluator)) {
            if (--count == 0) {
                return origin.parent();
            }
        }
        return selectNthElementBefore(origin.parent(), query, count);
    }
    return currentElement;
}

Nth next occurrence of an element matching the query:

public static Element selectNthElementAfter(Element origin, String query, int count) {
    Element currentElement = origin;
    Evaluator evaluator = QueryParser.parse(query);
    while ((currentElement = currentElement.nextElementSibling()) != null) {
        int val = 0;
        if (currentElement.is(evaluator)) {
            if (--count == 0)
                return currentElement;
            val++;
        }
        Elements elems = currentElement.select(query);
        if (elems.size() > val) {
            int childCount = elems.size() - val;
            int diff = count - childCount;

            if (diff == 0) {
                return elems.last();
            }
            if (diff > 0) {
                count -= childCount;
            }
            if (diff < 0) {
                return elems.get(childCount + diff);
            }
        }
    }
    if (origin.parent() != null && currentElement == null) {
        return selectNthElementAfter(origin.parent(), query, count);
    }
    return currentElement;
}

Usage:

Element elem = doc.getElementById("draft-discarded-42");

Element firstPrevInput = selectNthElementBefore(elem, "input", 1);
Element secPrevDiv = selectNthElementBefore(elem, "div", 2);
Element secNextDiv = selectNthElementAfter(elem, "div", 2);

System.out.println("#### First previous input ####");
System.out.println(firstPrevInput.toString());
System.out.println("##############################\n"); 
System.out.println("#### Second previous div ####");
System.out.println(secPrevDiv.toString());
System.out.println("#############################\n");
System.out.println("#### Second next div ####");
System.out.println(secNextDiv.toString());
System.out.println("#########################");

Output:

#### First previous input ####
<input id="previousInput" name="communitymode" type="checkbox">
##############################

#### Second previous div ####
<div class="fl" style="margin-top: 8px; height: 24px;">
 &nbsp;
</div>
#############################

#### Second next div ####
<div class="g-col -input"> 
    <input id="NextInput" name="communitymode"> 
</div>
#########################