读取文件（如果不存在），然后创建

Question

Honestly, I've searched a lot do this task so I ended up trying various methods but nothing worked until I ended up on this code. It works for me perfectly like it should, so I do not want to change my code.

The help I need is to put this code in a such a way that it begins to read a file, but if it the file doesn't exist then it will create a new file.

Code for saving data:

String data = sharedData.getText().toString();
try {
        fos = openFileOutput(FILENAME, MODE_PRIVATE);
        fos.write(data.getBytes());
        fos.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

Code for loading data:

FileInputStream fis = null;
        String collected = null;
        try {
            fis = openFileInput(FILENAME);
            byte[] dataArray = new byte [fis.available()];
            while (fis.read(dataArray) != -1){
                collected = new String(dataArray); 
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            try {
                fis.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

So If I add the saving data code in to the "FileNotFoundException" catch of the loading data part then could I achieve what I want?

Answer 1

Add

File file = new File(FILENAME);
if(!file.exists())
{  
   file.createNewFile()
   // write code for saving data to the file
}

above

fis = openFileInput(FILENAME);

This will check if there exists a File for the given FILENAME and if it doesn't it will create a new one.

Answer 2

If you're working on Android , why don't you use the API's solution for saving files ?

Quoting:

String filename = "myfile";
String string = "Hello world!";
FileOutputStream outputStream;

try {
  outputStream = openFileOutput(filename, Context.MODE_PRIVATE);
  outputStream.write(string.getBytes());
  outputStream.close();
} catch (Exception e) {
  e.printStackTrace();
}

You should really read the whole document, they explain pretty well the basic ways of creating or accessing files, you can also check the different ways of storing data .

But regarding your original question:

So If I add the saving data code in to the "FileNotFoundException" catch of the loading data part then could I achieve what I want?

Yes, you could achieve it.

Answer 3

Try this one:

public static void readData() throws IOException
{
    File file = new File(path, filename);
    if (!file.isFile() && !file.createNewFile()){
        throw new IOException("Error creating new file: " + file.getAbsolutePath());
    }

    BufferedReader r = new BufferedReader(new FileReader(file));
    try {
        // ...
        // read data
        // ...
    }finally{
        r.close();
    }
}

Ref: Java read a file, if it doesn't exist create it