Java Utility Class vs. Service

java static service utility
djunforgetable picture djunforgetable · May 16, 2009 · Viewed 29.7k times · Source

What's the difference in Java between a utility class (a class with static methods) and a Service class (a class with public methods that provides a "service"). For example, one can argue that a cryptographic object (providing methods to encrypt, decrypt, hash or get a salt value) is a Service provider, but many group this functionality into a Utility class with static methods, like CryptoUtil.encrypt(...). I'm trying to figure out which way follows better "design". Thoughts?

Answer

erickson picture erickson · May 16, 2009

Different behaviors can be obtained by using different service objects. Static methods in a utility class can't be swapped out. This is extremely useful for testing, changing implementations, and other purposes.

For example, you mention a CryptoUtil with an encrypt method. It would extremely useful to have different objects that could support different encryption strategies, different message recipients, etc.

Related questions

What does the 'static' keyword do in a class?

To be specific, I was trying this code: package hello; public class Hello { Clock clock = new Clock(); public static void main(String args[]) { clock.sayTime(); } } But it gave the error Cannot access non-static field in static method main So I …

Read More
Mocking static methods with Mockito

I've written a factory to produce java.sql.Connection objects: public class MySQLDatabaseConnectionFactory implements DatabaseConnectionFactory { @Override public Connection getConnection() { try { return DriverManager.getConnection(...); } catch (SQLException e) { throw new RuntimeException(e); } } } I'd like to validate the parameters passed to DriverManager.getConnection, …

Read More
What is the reason behind "non-static method cannot be referenced from a static context"?

The very common beginner mistake is when you try to use a class property "statically" without making an instance of that class. It leaves you with the mentioned error message: You can either make the non static method static or …

Read More