Jsoup-从网站获取某些属性

Question

Recently I've started with Jsoup and ve found this sample code.Because I'm newb I can't figure out how does this find all links from website.Could anyone explain me what happens in for loop? Mostly, I've never used this syntax of for loop before, so it's little bit confusing for me.I don't certainly understand what loop contains.Thank you!

    Elements links = doc.select("a[href]");
    for (Element link : links) {

        // get the value from href attribute
        System.out.println("\nlink : " + link.attr("href"));
        System.out.println("text : " + link.text());

    }

Answer 1

This is because Elements implements Iterable<Element>

( org.jsoup.select.Elements and java.lang.Iterable )

So when you use the for syntax you loop over your Elements links, which is effectively a List of type Element . The "Element link" is the local variable assigned to each element in 'links' as you iterate.

For further information, see:

http://jsoup.org/apidocs/org/jsoup/select/Elements.html and http://jsoup.org/apidocs/index.html

Answer 2

As the names suggest, the classes Elements and Element are similar. One consist of a single element that has been selected, and the other one is a collection of multiple elements that are grouped together.

Elements links consists of Element -objects that have been selected.

The Elements class implements the following interfaces in java:

Cloneable, Iterable< Element>, Collection< Element>, List< Element>.

The Elements class is implemented using ArrayList<Element> , thus it is easy to add and remove Element objects from the Elements collection.

When it comes to the for -loop it is a simple way to iterate over each Element object in the Elements collection called links.

The loop will iterate through the collection, and assign the variable link to the current Element object in the collection called links . Inside the for -loop the content of the current link will be printed, and the loop starts over with the next Element object in the collection.

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The syntax of this loop is often called a for-each loop, since it iterates over each object in a list or collection.

Read up on it here !

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Look through the Jsoup API docs to learn more about how to use it!

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If you want to learn more about how Jsoup is implemented, take a look at the source code !