Question

我在两个不同的文件中有两个java类（Crawler.java和A2ZurlRead.java）。在A2ZUrlRead.java里面我有以下内容：

 private LinkedList<String> issuesUrlsToVisit; // A queue of issues URLs to
                                                // visit
...

public A2ZUrlReader(String name) throws IOException {
    // Grab all actual issues urls into new queue.
    this.issuesUrlsToVisit = new LinkedList<String>();
            readContent();
    ....
}
...
...
public void readContent() throws IOException {
    ....
    ....
    // Add it LinkedList
    issuesUrlsToVisit.add("http://www.sourceforge.com" + url);
    ...
}

// return set of collected actual issues' urls
public LinkedList<String> getIssuesUrls() {
    return this.issuesUrlsToVisit;
}

在第二个类文件“Crawler.java”上我创建了A2ZUrlRead.java的对象，如下所示：

private void read(String urlpath) {

    System.out.println("Reading ... " + urlpath);
    try {
        // Grab the URLs content for issues
        A2ZUrlReader url = new A2ZUrlReader(urlpath);
        this.issuesURLsToVistit = url.getIssuesUrls();
        ...
    } catch (Exception e) {
        // System.out.println("Problem reading from " + urlpath + " " + e);
        // e.printStackTrace();
    }
}

public LinkedList<String> getIssuesURLs(){
    return this.issuesURLsToVistit;
}
public void print(){
    System.out.println("here !!");
    while(!this.issuesURLsToVistit.isEmpty()){
        String temp = this.issuesURLsToVistit.removeFirst();
        System.out.println(temp);
    }
}

从主函数我试图使用print（）方法打印LinkedList值，但它显示空结果？!!我试图从原始类打印LinkedList值成功!!

任何人都可以帮忙......

Answer 1

您正在构建对象，但在调用getIssuesUrls()之前从不调用填充链接列表的方法。

这样的事可能吗？

A2ZUrlReader url = new A2ZUrlReader(urlpath);
url.readContent();
this.issuesURLsToVistit = url.getIssuesUrls();

如何在类之间传递java中的LinkedList对象

1 个答案: