Android Internal/Externak Storage

Save data to Internal and External Storage(Android)

public class MainActivity extends AppCompatActivity {

   public static final String FILENAME = "myfile";
   private EditText mInput;
   private TextView mFromInternal;
   private TextView mFromExternal;
   private Switch mIsExternalSwitch;
   private Button mDelete;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);

       initUI();

       mIsExternalSwitch.setEnabled(isExternalStorageAvailable());

       mInput.setOnEditorActionListener(new TextView.OnEditorActionListener() {
           @Override
           public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
               if (actionId == EditorInfo.IME_ACTION_DONE) {
                   String text = v.getText().toString();
                   saveToFile(text, mIsExternalSwitch.isChecked());
                   updateTextViews();
               }
               return false;
           }
       });

       mDelete.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               deleteFile(mIsExternalSwitch.isChecked()));
   updateTextViews();
           }
       });

       updateTextViews();

   }

   private void deleteFile(boolean isExternal) {
       if (isExternal) {
           File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath(), FILENAME);
           if (file.delete()) {
               Toast.makeText(this, "deleted from external", Toast.LENGTH_SHORT).show();
           }

       } else {
           deleteFile(FILENAME);
           Toast.makeText(this, "deleted from internal", Toast.LENGTH_SHORT).show();
       }

   }

   private void updateTextViews() {
       mFromInternal.setText(readFromInternalFileIfOption());
       mFromExternal.setText(readFromExternalFileIfOption());
   }

   private String readFromExternalFileIfOption() {
       File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath(), FILENAME);
       try (BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file)))) {
           StringBuilder stringBuilder = new StringBuilder();
           String string;
           while ((string = reader.readLine()) != null) {
               stringBuilder.append(string).append("\n");
           }

           return stringBuilder.toString();
       } catch (FileNotFoundException e) {
           e.printStackTrace();
           Toast.makeText(this, "File not found", Toast.LENGTH_SHORT).show();
       } catch (IOException e) {
           e.printStackTrace();
           Toast.makeText(this, "Can't read from file", Toast.LENGTH_SHORT).show();
       }
       return "";

   }

   private void initUI() {
       mFromInternal = findViewById(R.id.tv_from_internal_file);
       mFromExternal = findViewById(R.id.tv_from_external_file);
       mIsExternalSwitch = findViewById(R.id.switch_is_external);
       mInput = findViewById(R.id.et_some_text);
       mDelete = findViewById(R.id.btn_delete_file);
   }

   private void saveToFile(String text, boolean isInExternal) {
       if (isInExternal) {
           saveToExternalFile(text);
       } else {
           saveToInternalFile(text);
       }
   }

   private boolean isExternalStorageAvailable() {
       String state = Environment.getExternalStorageState();
       return state.equals(Environment.MEDIA_MOUNTED);
   }

   private String readFromInternalFileIfOption() {
       try (BufferedReader reader = new BufferedReader(new InputStreamReader(openFileInput(FILENAME)))) {
           StringBuilder stringBuilder = new StringBuilder();
           String string;
           while ((string = reader.readLine()) != null) {
               stringBuilder.append(string).append("\n");
           }

           return stringBuilder.toString();
       } catch (FileNotFoundException e) {
           e.printStackTrace();
           Toast.makeText(this, "File not found", Toast.LENGTH_SHORT).show();
       } catch (IOException e) {
           e.printStackTrace();
           Toast.makeText(this, "Can't read from file", Toast.LENGTH_SHORT).show();
       }
       return "";
   }

   private void saveToInternalFile(String text) {
       try {
           String textToWrite = text + "\n";
           FileOutputStream outputStream = openFileOutput(FILENAME, Context.MODE_APPEND);
           outputStream.write(textToWrite.getBytes());
           outputStream.close();
           Toast.makeText(this, "written to internal", Toast.LENGTH_SHORT).show();
       } catch (Exception e) {
           e.printStackTrace();
       }
   }

   private void saveToExternalFile(String text) {
       try {
           String textToWrite = text + "\n";
           File file = new File(Environment.getExternalStorageDirectory(), FILENAME);
           FileOutputStream outputStream = new FileOutputStream(file, true);
           outputStream.write(textToWrite.getBytes());
           outputStream.close();
           Toast.makeText(this, "written to external", Toast.LENGTH_SHORT).show();
       } catch (FileNotFoundException e) {
           e.printStackTrace();
       } catch (IOException e) {
           e.printStackTrace();
       }
   }