包含不适用于（“ \\\\ +”）的方法

Question

I`m trying to write a Calculator app for android. for 4 main operators (-*/+) I used this method and for 3 of them it work without out any problems but for + operator it cannot recognize the + sign in the string i through at it. he is my code for / and + operators :

case R.id.buttonEql:
            current=show.getText().toString();
           if(current.contains("/"))
           { current+=input.getText().toString();
               show.setText(current);
              parts  = current.split("/");
           firstNumber = Integer.parseInt(parts[0]);
           secondNumber = Integer.parseInt(parts[1]);
              operationResult = firstNumber/secondNumber;
               show.setText("");
               show.setText(String.valueOf(operationResult));
               input.setText("0");
           }
           else if (current.contains("\\+"))
           {current=show.getText().toString();
               current+=input.getText().toString();
               show.setText(current);
               parts  = current.split("\\+");
               firstNumber = Integer.parseInt(parts[0]);
               secondNumber = Integer.parseInt(parts[1]);
               operationResult = firstNumber+secondNumber;
               show.setText("");
               show.setText(String.valueOf(operationResult));
               input.setText("0");}

Answer 1

In else if condition, what about doing just current.contains("+").

you are passing a regular expression (escaping it) which you should not for String contains function. Check on Java API Doc for String

Answer 2

Please, use contains() without escaping and split() with escaping

current.contains("+")

current.split("\\+")