java - 列表中始终显示最后一个元素的信息(Java)

Question

我有一些列表，其中包含一些 Apk 文件的信息:

static ContentAndDAO contentAndDao = new ContentAndDAO();

public static void main(String[] args) 
{
    int manifestNum;
    long contentId = 111111;
    long devFileId = 222222;
    List<DevFile> fileList;
    List<DevSupport> supports = null;
    List<ContentDev> contentList = new ArrayList<ContentDev>(); 
    ContentDevDAO contentDevDao = new ContentDevDAO();
    DevFileDAO devFileDao = new DevFileDAO();       
    ManifestMethods manifestMethods = new ManifestMethods();
    DevFile apkFile = null;

    try 
    {   
        manifestNum = 1;

        File dir = new File("C:\\Users\\lenovo 01\\Desktop\\basari\\buulkcontent\\klasorlenen");
        String[] extensions = new String[] {"apk"};
        List<File> files = (List<File>) FileUtils.listFiles(dir, extensions, true);         
        Collections.sort(files);
        for(File file : files)
        {           
            apkFile = new DevFile();
            fileList = new ArrayList<DevFile>();

            if(file.getName().contains(".apk"))
            {                   
                FileInputStream fis = new FileInputStream(new File(file.getAbsolutePath()));
                String apkMd5 = DigestUtils.md5Hex(fis);
                fis.close();

                System.out.println(file);
                System.out.println(file.length());
                System.out.println(apkMd5.toUpperCase());
                System.out.println(contentId);

                apkFile.setByteSize(file.length()); 
                apkFile.setUrl("/file/getContent/" + contentDevDao.createId(contentId) + "/" + apkMd5.toUpperCase() + "/apk");                  
                apkFile.setThumbnailUrl("/file/getContent/" + contentDevDao.createId(contentId) + "/" + apkMd5.toUpperCase() + "/apk");
                apkFile.setDeleteUrl("/file/deleteContent/" + contentDevDao.createId(contentId) + "/" + apkMd5.toUpperCase() + "/apk");
                apkFile.setFileHash(apkMd5.toUpperCase());
                apkFile.setFilePath("content/" + contentDevDao.createId(contentId) + "/" + apkMd5.toUpperCase() + ".apk");                                                              
                apkFile.setFileName(manifestMethods.getApplicationName(manifestNum).replaceAll(" ", "-") + ".apk");
                apkFile.setName(manifestMethods.getApplicationName(manifestNum).replaceAll(" ", "-"));                      
                apkFile.setPackageVersion(manifestMethods.getVersionName(manifestNum));                     
                apkFile.setPackageName(manifestMethods.getPackageName(manifestNum));                    
                apkFile.setPackageVersionCode(manifestMethods.getVersionCode(manifestNum));                     
                apkFile.setSdkVersion(manifestMethods.getSdkVersion(manifestNum));

                contentId++;
                devFileId++;
                manifestNum++;     
            }           
        }

        for(int y = 1; y <= 53; y++)
        {               
            manifestNum = 1;
            fileList = new ArrayList<DevFile>();

            DevFile file = new DevFile();
            ContentDev content = new ContentDev();

            /* some DevFile file addings */

            fileList.add(file);                 
            content.setDevFiles(fileList);
            contentList.add(content);
        }                       
    }   
    catch(Exception e) 
    {
        e.printStackTrace();
    }
}

当我将信息一一打印到控制台时，它按照我想要的方式显示。但在列表中，它总是只显示最后添加的 apk 文件的包名、字节大小、哈希值等。当然我不希望这样。怎么了？

注意:请不要介意代码缺乏可读性和模块化。我是面向对象结构的新手。

Answer 1

您在循环的每次迭代中创建一个新列表:

    for(int y = 1; y <= 53; y++)
    { 
        fileList = new ArrayList<DevFile>();
        DevFile file = new DevFile();
        ContentDev content = new ContentDev();

        /* some DevFile file addings */

        fileList.add(file);  
        ...

这意味着只有最后一个文件才会出现在该列表的最后。

将其更改为:

    fileList = new ArrayList<DevFile>();
    for(int y = 1; y <= 53; y++)
    { 
        DevFile file = new DevFile();
        ContentDev content = new ContentDev();

        /* some DevFile file addings */

        fileList.add(file);  
        ...

此外，我发现您在另一个循环中创建了 DevFile 实例，但从未对它们执行任何操作。难道不应该将它们添加到列表中吗？