What does the error "should check the method return value" mean?

Question

I am writing an application in Java using Swing. I am trying to convert the value in the text field txtDay to uppercase before evaluating the value in the below switch statement.

txtDay.getText().toUpperCase();

switch(txtDay.getText()){
    case "SUNDAY":
        //do something
        break;
    case "MONDAY":
        //do something
        break;
    case "TUESDAY":
        //do something
        break;
    case "WEDNESDAY":
        //do something
        break;
    case "THURSDAY":
        //do something
        break;
    case "FRIDAY":
        //do something
        break;
    case "SATURDAY":
        //do something
        break;
    default:
        //do something
        break;
}

Though at the first line (txtDay.getText().toUpperCase()), I am receiving an error saying "Should check the method return value".

What does this mean? Any tips on how to resolve this?

Answer 1

It's not an error but a warning. It says that you are not using the result of the operation. Strings being immutable, you need something like:

txtDay.setText(txtDay.getText().toUpperCase());

to get the result you expect.