Cut.java

package org.softlang.company.features;

import org.apache.xpath.XPathAPI;

import org.w3c.dom.Document; // DOM trees
import org.w3c.dom.Element; // DOM subtrees
import org.w3c.dom.NodeList; // Lists of DOM subtrees

import javax.xml.transform.TransformerException;

/**
 * Cut all or some salaries of a company in half
 */
public class Cut {

    public static void cutSalaries(Document doc, String xpath) 
        throws TransformerException {

        // Get the matching elements
        NodeList nodelist = XPathAPI.selectNodeList(doc, xpath);

        // Process the elements in the nodelist
        for (int i=0; i<nodelist.getLength(); i++) {

            // Get element
            Element elem = (Element)nodelist.item(i);

            // Transform content of element
            double before = Double.parseDouble(elem.getTextContent());
            double after = before / 2;
            elem.setTextContent(Double.toString(after));
        }
    }

    public static void cutAllEmployees(Document doc) 
        throws TransformerException {
        cutSalaries(doc, "//salary");
    }

    public static void cutManagersOnly(Document doc)
        throws TransformerException {
        cutSalaries(doc, "//manager/salary");
    }

}