How to avoid premature initialization if the variable is only used inside of a scope

Question

It seems that avoiding premature initialization is a good programming practice.

I'm using PMD add-on for Eclipse, and I have had some "Found 'DD'-anomaly for variable 'var'". I know what this anomaly means. It means that a variable is prematurely initialized (the initialized value is never used).

However, I'm stuck with the following problem.

This is an general example of what I want to do.

String var = null;

if (someCondition()) {
    Object a;
    //some treatment on a
    var = "some value" + a.toString();
}
else {
    Object b;
    //some treatment on b
    var = "some other value" + b.toString();
}

return var;

And this would be the specific example of what I want to do :

String token = null;
String authorization = getAuthorization(token);

if (authorization != null) {
    String[] parts = authorization.split(" ");
    if (parts.length == 2 && "Bearer".equals(part[0])) {
        token = parts[1];
    }
}
return token;

.

The problem is that the variable is only used inside of a scope (in this case inside of the if block or the else block), but it is also the value to return. So if I declare it inside the if block or the else block to avoid premature initialization, then the variable won't exist outside of those blocks and I won't be able to return it.

I also want to avoid using multiple return statement, because that would cause another anomaly from PMD.

Is there a way to solve my problem while avoiding premature initialization?

Answer 1

Use a single LoC for this:

return someCondition() ? "some value" : "some other value";

---

The code in here:

String token;
String authorization = getAuthorization(token);

if (authorization != null) {
    String[] parts = authorization.split(" ");
    if (parts.length == 2 && "Bearer".equals(part[0])) {
        token = parts[1];
    }

return token;

In this case, you should initialize the variable with a default value, then initialize it wherever you need to:

String token = "";
String authorization = getAuthorization(token);
if (authorization != null) {
    String[] parts = authorization.split(" ");
    if (parts.length == 2 && "Bearer".equals(part[0])) {
        token = parts[1];
    }
} //I assume there's a missing closing bracket here...
return token;

Also, I would move "Bearer" into an static final String variable in order to avoid using literal strings directly in the code.

Answer 2

You could simply skip the initialization and leave the variable uninitialized. The JVM will initialize it implicitly with null. But this works only, if you can guarantee, that the variable will eventually be initialized in the following control flow. You may declare it final, indicating that it will only be assigned once. Positive side effect, the Eclipse compiler will indicate an error if one control flow exists, where variable is not assigned.

final String var;

if (someCondition()) {
   var = "some value";
}
else {
   var = "some other value";
}

return var;

Answer 3

For the problem "Avoid using redundant field initializer for" the premature initialization on the field of a class, remove the initialization of fields. String token = null; String token; (quit initialization)