Are static methods inherited in Java

Question

I was reading A Programmer   s Guide to Java    SCJP Certification by Khalid Mughal   In the Inheritance chapter  it explains that     Inheritance of members is closely tied to their declared   accessibility  If a superclass member is accessible by its simple name   in the subclass  without the use of any extra syntax like super   that   member is considered inherited   It also mentions that static methods are not inherited  But the code below is perfectlly fine   class A       public static void display                 System out println  Inside static method of superclass             class B extends A       public void show                    This works - accessing display   by its simple name -            meaning it is inherited according to the book          display              How am I able to directly use display   in class B  Even more  B display   also works   Does the book s explanation only apply to instance methods

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Static method is inherited in subclass but it is not polymorphism  When you writing the implementation of static method  the parent s class method is over hidden  not overridden  Think  if it is not inherited then how you can be able to access without classname staticMethodname

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We can declare static methods with same signature in subclass  but it is not considered overriding as there won   t be any run-time polymorphism Because since all static members of a class are loaded at the time of class loading so it decide at compile time overriding at run time  Hence the answer is    No

User · Answer

Static members will not be inherited to subclass because inheritance is only for non-static members    And static members will be loaded inside static pool by class loader  Inheritance is only for those members which are loaded inside the object

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Static methods in Java are inherited  but can not be overridden  If you declare the same method in a subclass  you hide the superclass method instead of overriding it  Static methods are not polymorphic  At the compile time  the static method will be statically linked   Example   public class Writer       public static void write             System out println  Writing             public class Author extends Writer       public static void write             System out println  Writing book             public class Programmer extends Writer        public static void write             System out println  Writing code               public static void main String   args            Writer w   new Programmer            w write             Writer secondWriter   new Author            secondWriter write             Writer thirdWriter   null          thirdWriter write             Author firstAuthor   new Author            firstAuthor write              You ll get the following   Writing Writing Writing Writing book

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If that s what the book really says  it s wrong  1   The Java Language Specification  8 4 8 states      8 4 8 Inheritance  Overriding  and Hiding      A class C inherits from its direct superclass all concrete methods m  both static and instance  of the superclass for which all of the following are true          m is a member of the direct superclass of C    m is public  protected  or declared with package access in the same package as C    No method declared in C has a signature that is a subsignature    8 4 2  of the signature of m        1  It doesn t say that in my copy  1st edition  2000

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Static members are universal members  They can be accessed from anywhere

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Many have voiced out their answer in words  This is an extended explanation in codes   public class A       public static void test             System out println  A              public static void test2             System out println  Test             public class B extends A       public static void test             System out println  B                Called statically A test    B test    System out println        Called statically  testing static inheritance A test2    B test2    System out println        Called via instance object A a   new A    B b   new B    a test    b test    System out println        Testing inheritance via instance call a test2    b test2    System out println        Testing whether calling static method via instance object is dependent on compile or runtime type   A  b  hi    System out println        Testing whether null instance works A nullObj   null  nullObj hi      Results   A B  Test Test  A B  Test Test  A  A   Therefore  this is the conclusion    When we call the static in a static manner via    it will look for the static defined in that class  or the class nearest to that in the inheritance chain  This proves that static methods are inherited  When static method is called from an instance  it calls the static method defined in the compile-time type  Static method can be called from a null instance  My guess is that the compiler will use the variable type to find the class during compilation  and translate that to the appropriate static method call

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You can override static methods  but if you try to use polymorphism  then they work according to class scope Contrary to what we normally expect    public class A        public static void display            System out println  in static method of A             public class B extends A        void show            display                public static void display            System out println  in static method of B             public class Test        public static void main String   args           B obj  new B            obj show             A a obj new B            a obj display                  IN first case  o p is the  in static method of B    successful override  In 2nd case   o p is  in static method of A    Static method - will not consider polymorphism

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This concept is not that easy as it looks  We can access static members without inheritance  which is HasA-relation  We can access static members by extending the parent class also  That doesn t imply that it is an ISA-relation  Inheritance   Actually static members belong to the class  and static is not an access modifier  As long as the access modifiers permit to access the static members we can use them in other classes  Like if it is public then it will be accessible inside the same package and also outside the package  For private we can t use it anywhere  For default  we can use it only within the package  But for protected we have to extend the super class  So getting the static method to other class does not depend on being Static  It depends on Access modifiers  So  in my opinion  Static members can access if the access modifiers permit  Otherwise  we can use them like we use by Hasa-relation  And has a relation is not inheritance  Again we can not override the static method  If we can use other method but cant override it  then it is HasA-relation  If we can t override them it won t be inheritance So the writer was 100  correct

User · Answer

B display   works because static declaration makes the method member to belong to the class  and not any particular class instance  aka Object   You can read more about it here   Another thing to note is that you cannot override a static method  you can have your sub class declare a static method with the same signature  but its behavior may be different than what you d expect  This is probably the reason why it is not considered inherited  You can check out the problematic scenario and the explanation here

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All the public and protected members can be inherited from any class while the default or package members can also be inherited from the class within the same package as that of the superclass  It does not depend whether it is static or non static member   But it is also true that static member function do not take part in dynamic binding  If the signature of that static method is same in both parent and child class then concept of Shadowing applies  not polymorphism

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All methods that are accessible are inherited by subclasses    From the Sun Java Tutorials      A subclass inherits all of the public and protected members of its parent  no matter what package the subclass is in  If the subclass is in the same package as its parent  it also inherits the package-private members of the parent  You can use the inherited members as is  replace them  hide them  or supplement them with new members   The only difference with inherited static  class  methods and inherited non-static  instance  methods is that when you write a new static method with the same signature  the old static method is just hidden  not overridden   From the page on the difference between overriding and hiding        The distinction between hiding and overriding has important implications  The version of the overridden method that gets invoked is the one in the subclass  The version of the hidden method that gets invoked depends on whether it is invoked from the superclass or the subclass

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You can experience the difference in following code  which is slightly modification over your code   class A       public static void display             System out println  Inside static method of superclass             class B extends A       public void show             display               public static void display             System out println  Inside static method of this class             public class Test       public static void main String   args            B b   new B               prints  Inside static method of this class         b display             A a   new B               prints  Inside static method of superclass         a display              This is due to static methods are class methods   A display   and B display   will call method of their respective classes

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Static methods are inherited in Java but they don t take part in polymorphism  If we attempt to override the static methods they will just hide the superclass static methods instead of overriding them

[java] Are static methods inherited in Java?

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