Speeding up xpath

Question

I have a 1000 entry document whose format is something like:

Answer 1

If you need to parse huge but flat documents, SAX is a good alternative. It allows you to handle the XML as a stream instead of building a huge DOM. Your example could be parsed using a ContentHandler like this:

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.ext.DefaultHandler2;

public class ExampleHandler extends DefaultHandler2 {

    private StringBuffer chars = new StringBuffer(1000);

    private MyEntry currentEntry;
    private MyEntryHandler myEntryHandler;

    ExampleHandler(MyEntryHandler myEntryHandler) {
        this.myEntryHandler = myEntryHandler;
    }

    @Override
    public void characters(char[] ch, int start, int length)
            throws SAXException {
        chars.append(ch);
    }

    @Override
    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        if ("Entry".equals(localName)) {
            myEntryHandler.handle(currentEntry);
            currentEntry = null;
        }
        else if ("n1".equals(localName)) {
            currentEntry.setN1(chars.toString());
        }
        else if ("n2".equals(localName)) {
            currentEntry.setN2(chars.toString());
        }
    }


    @Override
    public void startElement(String uri, String localName, String qName,
            Attributes atts) throws SAXException {
        chars.setLength(0);
        if ("Entry".equals(localName)) {
            currentEntry = new MyEntry();
        }
    }
}

If the document has a deeper and more complex structure, you're going to need to use Stacks to keep track of the current path in the document. Then you should consider writing a general purpose ContentHandler to do the dirty work and use with your document type dependent handlers.