Java Accessing a class within a package which is the better way

Question

If I access a class within a package using fully qualified name  without importing it  whether it saves any memory   Using fully qualified class name     java lang Math sqrt x     Import package    import java lang Math   Math sqrt x     which is the better way   import the package or access using fully qualified name    Thanking you

User · Answer

No  it doesn t save you memory   Also note that you don t have to import Math at all  Everything in java lang is imported automatically   A better example would be something like an ArrayList  import java util ArrayList       ArrayList lt String gt  i   new ArrayList lt String gt       Note I m importing the ArrayList specifically  I could have done   import java util       But you generally want to avoid large wildcard imports to avoid the problem of collisions between packages

User · Answer

Import package is for better readability   Fully qualified class has to be used in special scenarios  For example  same class name in different package  or use reflect such as Class forName

User · Answer

There is no performance difference between importing the package or using the fully qualified class name  The import directive is not converted to Java byte code  consequently there is no effect on runtime performance  The only difference is that it saves you time in case you are using the imported class multiple times  This is a good read here

User · Answer

They re equivalent   The access is the same   The import is just a convention to save you from having to type the fully-resolved class name each time   You can write all your Java without using import  as long as you re a fast touch typer   But there s no difference in efficiency or class loading

User · Answer

As already said  on runtime there is no difference  in the class file it is always fully qualified  and after loading and linking the class there are direct pointers to the referred method   and everything in the java lang package is automatically imported  as is everything in the current package   The compiler might have to search some microseconds longer  but this should not be a reason - decide for legibility for human readers   By the way  if you are using lots of static methods  from Math  for example   you could also write  import static java lang Math      and then use  sqrt x    directly  But only do this if your class is math heavy and it really helps legibility of bigger formulas  since the reader  as the compiler  first would search in the same class and maybe in superclasses  too   This applies analogously for other static methods and static variables  or constants   too

[java] Java : Accessing a class within a package, which is the better way?

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