读取和修改文件夹中的每个文件 - Java [重复]

Question

我有一个包含 1000 个文件的文件夹。每个文件包含不同行数的文本。我想要并试图实现的是读取“每个”文件并将所有行附加到 1 行中（也就是说，我希望每个文件都有一行文本）。

这是我尝试过的，但它只打印文件名而不影响对文件的任何更改...

String line = "";
try{
    file = new FileReader(filename);
    BufferedReader reader = new BufferedReader (file);
    while ((line = reader.readLine()) != null){
        allLine.append(line);              
    }
    //System.out.println(allLine);
} catch (IOException e) {
    throw new RuntimeException("File not found");
} 
return allLine.toString();

FileWriter op = null;
op = new FileWriter(fileName);
BufferedWriter wryt = new BufferedWriter(op);
wryt.write(s);
wryt.flush();

if(op != null){
    op.close();
}

File[] lOfiles = folder.listFiles();

for (int i = 0; i< lOfiles.length; i++){
    if(lOfiles[i].isFile()){
        System.out.println(lOfiles[i].getName());
        ReadLines rd = new ReadLines();
        String rw = rd.readtxtFile(lOfiles[i].toString());
        rd.writetxtFile(lOfiles[i].getName(), rw);
    }
}

Answer 1

    try {
        File folder = new File("yourfolderpath");
        File out = new File("outputfile.txt");
        try(BufferedWriter bw = new BufferedWriter(new FileWriter(out))){
            for(File f: folder.listFiles()) {
                BufferedReader br = new BufferedReader(new FileReader(f));
                for(String line = br.readLine(); line!=null; line=br.readLine()) {
                    bw.write(line);
                }
            }           
        }
    } catch (IOException e) {
        e.printStackTrace();
    }