是否应该实例化通用类？

Question

I am currently working on a new project for university and was curious as to the best way to handle a class I've created to perform utility operations such as hashing passwords.

Should the utility class contain static methods so that I call them like

Utilities.hashPassword(password,salt); 

Or should I create a new instance for each call

new Utilities().hashPassword(password, salt);

Right now I have a new instance for each call to a function inside that class, but im concerned about the performance implications of this and am wondering if its even nessecary to do.

My original reason for instantiating them was because I wasn't sure how thread-safety worked and was concerned that multiple users calling the same static function would cause problems. After reading some material on java concurrency I'm now pretty sure that even if the method is static it would be thread-safe.

Should I change them all to static methods? Would this improve performance? Right now my test server buckles under load.

Thanks

Answer 1

Thread-safety does not care if a method is static or a true member method. Thread-safety cares about concurrent modification to data. So, if your method is updating some generic data structure, you are NOT thread-safe just by making it static.

Arguments against "static": anything that is static is very hard to mock within unit tests. So be really careful about making stuff static just for convenience.

Regarding the performance aspect: object creation is very cheap in java (not completely free, but cheap). In your case - you could keep it a member method - just avoid to throw away your utility object all the time.

Answer 2

Should I change them all to static methods?

Yes. Utility method should be static. Because, instead of new Utilities().hashPassword(password, salt); use only static import of hashPassword(password, salt) . Shorter and easier to read.

Would this improve performance?

Yes. Declaring static will save memory. It will also improve readability.

See also: Java: when to use static methods