Java Static Class

Question

I have a class full of utility functions  Instantiating an instance of it makes no semantic sense  but I still want to call its methods  What is the best way to deal with this  Static class  Abstract

User · Accepted Answer

Private constructor and static methods on a class marked as final

User · Answer

Sounds like you have a utility class similar to java lang Math  The approach there is final class with private constructor and static methods   But beware of what this does for testability  I recommend reading this article Static Methods are Death to Testability

User · Answer

Just to swim upstream  static members and classes do not participate in OO and are therefore evil   No  not evil  but seriously  I would recommend a regular class with a singleton pattern for access   This way if you need to override behavior in any cases down the road  it isn t a major retooling   OO is your friend  -   My   02

User · Answer

comment on the  private constructor  arguments  come on  developers are not that stupid  but they ARE lazy  creating an object then call static methods  not gonna happen   don t spend too much time to make sure your class cannot be misused  have some faith for your colleagues  and there is always a way to misuse your class no matter how you protect it  the only thing that cannot be misused is a thing that is completely useless

User · Answer

There s no point in declaring the class as static   Just declare its methods static and call them from the class name as normal  like Java s Math class   Also  even though it isn t strictly necessary to make the constructor private  it is a good idea to do so   Marking the constructor private prevents other people from creating instances of your class  then calling static methods from those instances    These calls work exactly the same in Java  they re just misleading and hurt the readability of your code

User · Answer

According to the great book  Effective Java    Item 4  Enforce noninstantiability with a private constructor  - Attempting to enforce noninstantiability by making a class abstract does not work   - A default constructor is generated only if a class contains no explicit constructors  so a class can be made noninstantiable by including a private constructor      Noninstantiable utility class public class UtilityClass          Suppress default constructor for noninstantiability     private UtilityClass             throw new AssertionError              Because the explicit constructor is private  it is inaccessible outside of the class  The AssertionError isn   t strictly required  but it provides insurance in case the constructor is accidentally invoked from within the class  It guarantees that the class will never be instantiated under any circumstances  This idiom is mildly counterintuitive  as the constructor is provided expressly so that it cannot be invoked  It is therefore wise to include a comment  as shown above   As a side effect  this idiom also prevents the class from being subclassed  All constructors must invoke a superclass constructor  explicitly or implicitly  and a subclass would have no accessible superclass constructor to invoke

User · Answer

Final class and private constructor  good but not essential  Public static methods

User · Answer

You can use  UtilityClass annotation from lombok https   projectlombok org features experimental UtilityClass

[java] Java: Static Class?

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