Jsoup - extracting data from an <a> tag, inside a <td> tag

问题

I want to extract data from a Web site, using Jsoup. The data are in a table.

HTML code:

<table><tr><td><a href="......">Pop.Density</a></td>
           <td>123</td></tr></table>

I want to print:

zip code...(taken from a text file): 123

I have the following exception:

Exception in thread "main" java.lang.NullPointerException

Any help would be appreciated. Thank you!

This is my code:

String s = br.readLine();
String str="http://www.bestplaces.net/people/zip-code/illinois/"+s;

org.jsoup.Connection conn = Jsoup.connect(str);
conn.timeout(1800000); 
Document doc = conn.get();

for (Element table : doc.select("table"))
{
    for (Element row : table.select("tr")) 
    {
    Elements tds = row.select("td");
    if (tds.size() > 1)
    {
        Element link = tds.get(0).select("a").first();
        String linkText = link.text();

        if (link.text().contains("Pop.Density"))
            System.out.println(s+","+tds.get(1).text());
        }
    }
}

UPDATE: If I modify the last if():

if (tds.get(0).select("a").text().contains("Pop.Density"))

I do not have any exceptions, but no output either.

回答1:

Assuming the shared html is not the real one being used, I think its throwing the exception when first TD doesn't have <a> tag. I think you need to update

  if (tds.size() > 1) 

as

  if (tds.size() > 1 && tds.get(0).select("a") != null 
                          && tds.get(0).select("a").first() ! null)

If this is not the case, sharing the line number of NullPointerException origin can help better finding the solution.

来源：https://stackoverflow.com/questions/12992325/jsoup-extracting-data-from-an-a-tag-inside-a-td-tag