Sort Java List/Map by order in which items are in an XML File

Question

What I'm looking to do is to sorta a Java List or Map in the order the items are in a XML File.

For Example

I have a list of function names as so:

1. functionOne
2. functionThree
3. functionTwo

The XML File looks like this:

<xml>
  <function>functionOne</function>
  <function>functionTwo</function>
  <function>functionThree</function>
</xml>

So I would like to sort the list so the function names are as so:

1. functionOne
2. functionTwo
3. functionThree

Now Im trying to do this for Variables as well, so there are around 500+ unique 'items'.

Does anyone have any idea how I can go about doing this? Now for the file that determines that sort order doesn't have to be XML it just what I use the most, it can be anything that can get the job done.

Thanks in advance for your time.

Answer 1

First, parse the XML file to build a Map<String,Integer> which maps the names to their ordinal position.

Then, you need a custom Comparator:

public class XMLComparator implements Comparator<String> {
    private Map<String,Integer> order;

    public XMLComparator(Map<String,Integer> desiredOrder) {
        order = desiredOrder;
    }

    public void compare(String s1, String s2) {
        return order.get(s1) - order.get(s2);
    }

}

then apply it to your list of variable names:

Collections.sort(variableNames, new XMLComparator(previouslyCreatedMap));

There's probably some edge cases to take care of, but that's the general idea.