this is a function to save strings to internal storage in android

save_text_storage.java

    public void save(View view) {
        String text1 = username.getText().toString();
        String text2 = password.getText().toString();

        text1 = text1 + " ";
        File file = null;
        FileOutputStream fileOutputStream = null;
        try {
            file=getFilesDir();
            fileOutputStream = openFileOutput("vivz.txt", Context.MODE_PRIVATE);
            fileOutputStream.write(text1.getBytes());
            fileOutputStream.write(text2.getBytes());

        } catch (FileNotFoundException e) {
            //e.printStackTrace();
            Log.d("VIVZ",e.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
        finally {
            try {
                fileOutputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        Toast.makeText(this,"Saved successfully " +file+"/vivz.txt",Toast.LENGTH_SHORT).show();
    }