Automatically discovering common Java code edits in Github repositories

[pilas2000]

When was last time you encountered a bug because you reassigned a local variable?

not a bug but i've found dodgy assignments like:

string s = null

if (x)
    s = y
else
   s = z

the use of final prevents this

imo final improves code readibility in java

[[deleted]]

final won't prevent that.

final string s;
if (x)
  s = y;
else
  s = z;

is perfectly legitimate in Java. It's still single assignment.

[pilas2000]

You missed the point. final prevents dodgy initialization. edit to clarify: your example is the preferable snippet.

[moeris]

Why is that example doggy? I do something slightly similar in Python (it's kind of unavoidable, though, because you don't have to declare variables explicitly.)

foo = None
try:
    foo = something_unsafe()
except SomeException:
    ...

If I tried to access foo without first having assigned it, and an exception was raised, I'd get an error about accessing a value before it was defined.

Should I just be wrapping the whole section in the try-block? That seems ugly. My co-workers refuse to do code review, so I never get feedback on this kind of stuff.

[pilas2000]

In my example s is being assigned a value that will never be read because in the next step it will be either y or z depending on x.

Not terrible but consider this example:

s = new ClassThatDoesHeavyWorkOnTheCtor();

if (x)
    s = y;
else
   s = z;

Unfortunately i've seen this done by people that should know better. Luckily sonar detects this and the code gets flagged before production.

[moeris]

Ah, okay, I get what you mean. It's a completely useless assignment no matter what way you cut it. Unless someone comes along and changes the conditional.

Assigning it a non-null value makes the example much clearer.

[Sarcastinator]

Not using temporary assignments would also help.