Question

我试图优化我的代码;它读取特定文件夹中的文件并在Windows中显示它们，然后进一步使用它们。一切都按预期工作，但当文件夹中有很多文件（如100+）时，加载内容真的很滞后。

有人可以给我建议如何优化这个功能吗？

private void ReloadScanFiles() {
        if (gsfCurRow != null) {
            ArrayList<FileInfo> newTreeFileInfoList = new ArrayList<FileInfo>();
            ArrayList<FileInfo> addTreeFileInfoList = new ArrayList<FileInfo>();
            ArrayList<String> delTreeFileNameList = new ArrayList<String>();

            File folder = new File(gsfCurRow.DOC_SOURCE_PATH);

            FileFilter fileFilter = new FileFilter() {
                public boolean accept(File file) {
                    return !file.isDirectory() && !file.isHidden();
                }
            };
/*          
            FilenameFilter fileFilter = new FilenameFilter() {
                public boolean accept(File dir, String name) {
                    return name.toLowerCase().endsWith(".pdf") ||
                           name.toLowerCase().endsWith(".jpeg") ||
                           name.toLowerCase().endsWith(".jpg") ||
                           name.toLowerCase().endsWith(".tiff") ||
                           name.toLowerCase().endsWith(".txt");                    
                }
            };
*/
            File[] listOfFiles = folder.listFiles(fileFilter);          

            for (int i = 0; i < listOfFiles.length; i++){
                FileInfo fileInfo = new FileInfo();

                fileInfo.Name = listOfFiles[i].getName();
                //fileInfo.Length = (long) listOfFiles[i].length();
                fileInfo.LastModified = (long) listOfFiles[i].lastModified(); //Long.parseLong("473", 10);

                newTreeFileInfoList.add(fileInfo);
            }


            //add new items
            for (FileInfo fileInfo: newTreeFileInfoList){                   
                boolean existsItem = false;

                if (actTreeFileInfoList != null){
                    for (FileInfo fileInfo1: actTreeFileInfoList){
                        if (fileInfo.Name.equals(fileInfo1.Name)) {
                            existsItem = true;
                            break;
                        }
                    }
                }


                if (!existsItem) {
                    addTreeFileInfoList.add(fileInfo);
                }
            }



            //delete non existing items

            if (actTreeFileInfoList != null){
                for (FileInfo fileInfo: actTreeFileInfoList){
                    boolean existsItem = false;

                    for (FileInfo fileInfo1: newTreeFileInfoList){
                        if (fileInfo.Name.equals(fileInfo1.Name)) {
                            existsItem = true;
                            break;
                        }
                    }


                    if (!existsItem) {
                        delTreeFileNameList.add(fileInfo.Name);
                    }
                }                   
            }

            actTreeFileInfoList = newTreeFileInfoList;



            //add items to tree
            for (FileInfo fileInfo: addTreeFileInfoList){
                TreeItem item = new TreeItem(tv, SWT.NONE); 
                //item.setText(new String[] {fileInfo.Name, Long.toString(fileInfo.Length), df.format(fileInfo.LastModified)});
                item.setText(new String[] {fileInfo.Name, null, df.format(fileInfo.LastModified)});             
                fileCount ++;                       
            }



            //delete item from tree
            //update locked by
            TreeItem [] items = tv.getItems();   
            for (TreeItem item: items){
                //delete
                if (delTreeFileNameList.contains(item.getText())) {
                    if (item.getChecked()) {
                        checkedFileCount --;                    
                    }
                    fileCount --;
                    item.dispose();
                }
                //update
                if (!item.isDisposed()){
                    Integer lock_idusr = null;
                    try {
                        lock_idusr = db.FileLockedBy(gsfCurRow.DOC_SOURCE_ID, item.getText());
                    } catch (SQLException e) {
                        e.printStackTrace();
                    }


                    if ((lock_idusr != null) && (!lock_idusr.equals(idusr))){
                        try {
                            item.setText(3, db.GetOpid(lock_idusr));
                        } catch (SQLException e) {
                            e.printStackTrace();
                        }
                        Color color = new Color(display,180, 0, 0);
                        item.setForeground(color);
                        item.setChecked(false);
                    } 
                    else{
                        item.setText(3, "");
                        Color color = new Color(display,0, 0, 0);
                        item.setForeground(color);                      
                    }
                }
            }

            BtnDocAssignEnabled();
            GenerateTreeStatusText();
        }
}

Answer 1

您所做的最明显的错误是：

        for (FileInfo fileInfo: newTreeFileInfoList){                   
            boolean existsItem = false;

            if (actTreeFileInfoList != null){
                for (FileInfo fileInfo1: actTreeFileInfoList){
                    if (fileInfo.Name.equals(fileInfo1.Name)) {
                        existsItem = true;
                        break;
                    }
                }
            }


            if (!existsItem) {
                addTreeFileInfoList.add(fileInfo);
            }
        }

对于每个新元素，您遍历整个旧条目列表以检查它是否已经在列表中。有了100个新文件，这将导致5050次迭代。您可以考虑使用带有文件名的Map作为键而不是ArrayList。您的支票将如下所示：

for (FileInfo fileInfo: newTreeFileInfoList){
    if (!actTreeFileInfoMap.containsKey(fileInfo.Name)) {
        actTreeFileInfoMap.put(fileInfo.Name, fileInfo);
    }
}

如果Map中的实际fileinfo不重要，您可以跳过整个检查并将新的fileInfo放入Map中。这将导致用新添加的一个替换之前添加的一个。

在读取文件时优化Java性能

1 个答案: