java JFileChooser（showSaveDialog）无法获取所选扩展文件的值

Question

我正在制作一个桌面应用程序，它有一个JFileChooser（ShowSaveDialog）功能。。 当我试图保存一个示例文本文件时，程序没有得到我选择的扩展名文件。。我正在尝试使用if-else或switch语句，但我不知道如果选择pdf、word或txt扩展名作为文件扩展名，我将使用什么命令来获取条件的字符串/Int值

public class Save {
    static boolean flag = false;
    public static void main(String[] args) throws IOException, SQLException {
        JFileChooser saveFile = new JFileChooser();
        saveFile.setDialogTitle("Save as"); 

        FileNameExtensionFilter File_ext_txt =
            new FileNameExtensionFilter("Text Documents(*.txt)", "txt");
        FileNameExtensionFilter File_ext_pdf =
            new FileNameExtensionFilter("PDF", "pdf");
        FileNameExtensionFilter File_ext_doc =
            new FileNameExtensionFilter("Word 97-2003 Document", "doc");
        saveFile.addChoosableFileFilter(File_ext_pdf);
        saveFile.addChoosableFileFilter(File_ext_doc);
        saveFile.addChoosableFileFilter(File_ext_txt);

        FileFilter extension = saveFile.getFileFilter();
        int userSelection = saveFile.showSaveDialog(null);
        File File_Path = saveFile.getSelectedFile();
        String fullPath = File_Path.getAbsolutePath();
        String Ext = null;
        if (userSelection == JFileChooser.APPROVE_OPTION){
            if(extension == File_ext_txt){
                Ext = "txt";
            }

            File save = new File(fullPath+"."+Ext);
            System.out.println(extension);
            flag = save.createNewFile();
        }
    }
}

Answer 1

我以前遇到过这个问题。这是我的一个程序中的一个实用函数，您可以使用它来代替JFileChooser.getSelectedFile，以获得扩展

/**
 * Returns the selected file from a JFileChooser, including the extension from
 * the file filter.
 */
public static File getSelectedFileWithExtension(JFileChooser c) {
    File file = c.getSelectedFile();
    if (c.getFileFilter() instanceof FileNameExtensionFilter) {
        String[] exts = ((FileNameExtensionFilter)c.getFileFilter()).getExtensions();
        String nameLower = file.getName().toLowerCase();
        for (String ext : exts) { // check if it already has a valid extension
            if (nameLower.endsWith('.' + ext.toLowerCase())) {
                return file; // if yes, return as-is
            }
        }
        // if not, append the first extension from the selected filter
        file = new File(file.toString() + '.' + exts[0]);
    }
    return file;
}