In below example I have created a save data app code in android. In this save data we can save our data and then load the back-up. In this I have also described how to make save data.

public class MainActivity extends Activity {
      EditText editText;
     TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        editText =(EditText)findViewById(R.id.edittext);
        textView =(TextView)findViewById(R.id.textview);
        textView.setVisibility(View.GONE);
    }

    public void writeMessage(View view)
    {
    String Message = editText.getText().toString();
        String file_name ="hello_file";
        try{
            FileOutputStream fileOutputStream =openFileOutput(file_name,MODE_PRIVATE);
            fileOutputStream.write(Message.getBytes());
            fileOutputStream.close();
            Toast.makeText(getApplicationContext(),"Message Saved",Toast.LENGTH_LONG).show();
            editText.setText("");


        }catch (FileNotFoundException e){
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
    public void readMessage(View view)
    {
        try{
           String Message;
            FileInputStream fileInputStream = openFileInput("hello_file");
            InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
            BufferedReader bufferedReader =new BufferedReader(inputStreamReader);
            StringBuffer stringBuffer =new StringBuffer();
            while((Message=bufferedReader.readLine())!=null)
            {
                stringBuffer.append(Message +"\n");

            }
            textView.setText(stringBuffer.toString());
            textView.setVisibility(View.VISIBLE);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }


    }




    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}