// 구구단 3단을 출력하는 Rx 코드
int dan = 3;
EditText guguEdit = (EditText)findViewById(R.id.guguEdit);
EditText guguResult = (EditText)findViewById(R.id.guguResult);

guguEdit.setText(Integer.toString(dan));
Observalbe.range(1, 9)
  .map(row -> dan + " * " + row " = " + (dan * row))
  .map(row -> row + row + '\n')
  .subscribe(guguResult::append);