Question

Often in code I get to scenarios I need a temporary variable – example:

String tempUserName = input.getUserName();
tempUserName = sanitzie(tempUserName);
validate(tempUserName);
// ... Do something else with tempUserName

String tempUserNickName = input.getUserNickName();
tempUserNickName = sanitzie(tempUserNickName);
validate(tempUserNickName);
// ... Do something else with tempUserNickName

...
...

I know that some people use a single temp variable for these kind of things:

String temp = input.getUserName();
temp = sanitzie(temp);
validate(temp);
// ... Do something else with temp

temp = input.getUserNickName();
temp = sanitzie(temp);
validate(temp);
// ... Do something else with temp

...
...

In my opinion – the way I write it is clearer and less error-prone.

My question is – are there any benefits for using the single temp variable from:

1. Memory consumption perspective
2. Performance perspective
3. Any other perspective

Lets limit the scope of the question to String variables only – but I’ll be happy to get a more general feedback.

Answer 1

My main answer to this would be if you have a series of those sorts of statements, I’d break the groupings out into a separate function you call. (Which would have just the one temp variable.) E.g.:

private String handleInput(String val) {
    val = sanitzie(val);
    validate(val);
    // ... Do something else with val

    return val;
}

Usage:

String finalPlaceForUserName     = handleInput(input.getUserName());
String finalPlaceForUserNickName = handleInput(input.getUserNickName());

…where handleInput might return null for invalid or dangerous input, etc. You may well have to parameterize handleInput more than above.

Answer the perspectives you raised:

Memory consumption perspective

I suppose technically, if there were only one temp variable, the memory from earlier on would be eligible for garbage collection earlier (e.g., while the method was running rather than afterward). But I doubt it makes any real-world difference.

Performance perspective

I can’t imagine so.

Any other perspective

We probably come down to style here, which is mostly a matter of personal preference. Again, I’d split it off into a function, which is kind of an end-run around the question. 🙂