FileIO

public class MainActivity extends Activity {
    private static final String FILE_NAME = "file_output.txt";
    private Button bt1, bt2;
    private TextView tv;
    private EditText et;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt1 = (Button) findViewById(R.id.bt1);
        bt2 = (Button) findViewById(R.id.bt2);
        tv = (TextView) findViewById(R.id.tv);
        et = (EditText) findViewById(R.id.et);
        bt1.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                savedInputDatatoFile();
            }
        });
        bt2.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                loadDataFromFile();
            }
        });
    }

    private void savedInputDatatoFile() {
        try {
            FileOutputStream fos = openFileOutput(FILE_NAME,
                    Context.MODE_PRIVATE);
            String inputFileContent = et.getText().toString();
            fos.write(inputFileContent.getBytes());
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void loadDataFromFile() {
        try {
            FileInputStream fis = openFileInput(FILE_NAME);
            byte[] buffer = new byte[1024];
            fis.read(buffer);
            String fileContent = EncodingUtils.getString(buffer, "UTF-8");
            tv.setText(fileContent);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}