What is the difference between a static method and a non-static method

Question

See the code snippets below   Code 1  public class A       static int add int i  int j            return i   j            public class B extends A       public static void main String args              short s   9          System out println add s  6              Code 2  public class A       int add int i  int j            return i   j            public class B extends A       public static void main String args          A a   new A            short s   9          System out println a add s  6              What is the difference between these code snippets  Both output 15 as an answer

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Well  more technically speaking  the difference between a static method and a virtual method is the way the are linked   A traditional  static  method like in most non OO languages gets linked wired  statically  to its implementation at compile time  That is  if you call method Y   in program A  and link your program A with library X that implements Y    the address of X Y   is hardcoded to A  and you can not change that   In OO languages like JAVA   virtual  methods are resolved  late   at run-time  and you need to provide an instance of a class  So in  program A  to call virtual method Y    you need to provide an instance  B Y   for example  At runtime  every time A calls B Y   the implementation called will depend on the instance used  so  B Y     C Y   etc    could all potential provide different implementations of Y   at runtime   Why will you ever need that  Because that way you can decouple your code from the dependencies  For example  say program A is doing  draw     With a static language  thats it  but with OO you will do B draw   and the actual drawing will depend on the type of object B  which  at runtime  can change to square a circle etc  That way your code can draw multiple things with no need to change  even if new types of B are provided AFTER the code was written  Nifty -

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A static method belongs to the class and a non-static method belongs to an object of a class  I am giving one example how it creates difference between outputs   public class DifferenceBetweenStaticAndNonStatic      static int count   0    private int count1   0     public DifferenceBetweenStaticAndNonStatic        count1   count1 1         public int getCount1         return count1         public void setCount1 int count1        this count1   count1         public static int countStaticPosition         count   count 1       return count                one can not use non static variables in static method so if we will        return count1 it will give compilation error  return count1                 public class StaticNonStaticCheck      public static void main String   args       for int i 0 i lt 4 i            DifferenceBetweenStaticAndNonStatic p  new DifferenceBetweenStaticAndNonStatic          System out println  static count position is    DifferenceBetweenStaticAndNonStatic count           System out println  static count position is    p getCount1             System out println  static count position is    DifferenceBetweenStaticAndNonStatic countStaticPosition              System out println  next case              System out println                     Now output will be     static count position is 0 static count position is 1 static count position is 1 next case    static count position is 1 static count position is 1 static count position is 2 next case    static count position is 2 static count position is 1 static count position is 3 next case

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Generally   static  no need to create object we can directly call using  ClassName methodname     Non Static  we need to create a object like  ClassName obj new ClassName   obj methodname

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If your method is related to the object s characteristics  you should define it as non-static method  Otherwise  you can define your method as static  and you can use it independently from object

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A static method belongs to the class   and a non-static method belongs to an   object of a class  That is  a   non-static method can only be called   on an object of a class that it   belongs to  A static method can   however be called both on the class as   well as an object of the class  A   static method can access only static   members  A non-static method can   access both static and non-static   members because at the time when the   static method is called  the class   might not be instantiated  if it is   called on the class itself   In the   other case  a non-static method can   only be called when the class has   already been instantiated  A static   method is shared by all instances of   the class  These are some of the basic   differences  I would also like to   point out an often ignored difference   in this context  Whenever a method is   called in C   Java C   an implicit   argument  the  this  reference  is   passed along with without the other   parameters  In case of a static method   call  the  this  reference is not   passed as static methods belong to a   class and hence do not have the  this    reference    Reference Static Vs Non-Static methods

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Simply put  from the point of view of the user  a static method either uses no variables at all or all of the variables it uses are local to the method or they are static fields  Defining a method as static gives a slight performance benefit

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Static methods are useful if you have only one instance  situation  circumstance  where you re going to use the method  and you don t need multiple copies  objects   For example  if you re writing a method that logs onto one and only one web site  downloads the weather data  and then returns the values  you could write it as static because you can hard code all the necessary data within the method and you re not going to have multiple instances or copies  You can then access the method statically using one of the following   MyClass myMethod    this myMethod    myMethod      Non-static methods are used if you re going to use your method to create multiple copies  For example  if you want to download the weather data from Boston  Miami  and Los Angeles  and if you can do so from within your method without having to individually customize the code for each separate location  you then access the method non-statically   MyClass boston   new MyClassConstructor     boston myMethod  bostonURL     MyClass miami   new MyClassConstructor     miami myMethod  miamiURL     MyClass losAngeles   new MyClassConstructor    losAngeles myMethod  losAngelesURL      In the above example  Java creates three separate objects and memory locations from the same method that you can individually access with the  boston    miami   or  losAngeles  reference  You can t access any of the above statically  because MyClass myMethod    is a generic reference to the method  not to the individual objects that the non-static reference created   If you run into a situation where the way you access each location  or the way the data is returned  is sufficiently different that you can t write a  one size fits all  method without jumping through a lot of hoops  you can better accomplish your goal by writing three separate static methods  one for each location

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Sometimes  you want to have variables that are common to all objects  This is accomplished with the static modifier   i e  class human - number of heads  1  is static  same for all humans  however human - haircolor is variable for each human   Notice that static vars can also be used to share information across all instances

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Basic difference is non static members are declared with out using the keyword  static   All the static members  both variables and methods  are referred with the help of class name  Hence the static members of class are also called as class reference members or class members    In order to access the non static members of a class we should create reference variable   reference variable store an object

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A static method belongs to the class itself and a non-static  aka instance  method belongs to each object that is generated from that class  If your method does something that doesn t depend on the individual characteristics of its class  make it static  it will make the program s footprint smaller   Otherwise  it should be non-static   Example   class Foo       int i       public Foo int i            this i   i             public static String method1            return  An example string that doesn t depend on i  an instance variable               public int method2            return this i   1     Depends on i           You can call static methods like this  Foo method1    If you try that with method2  it will fail  But this will work  Foo bar   new Foo 1   bar method2

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Another scenario for Static method      Yes  Static method is of the class not of the object  And when you don t want anyone to initialize the object of the class or you don t want more than one object  you need to use Private constructor and so the static method    Here  we have private constructor and using static method we are creating a object   Ex    public class Demo            private static Demo obj   null                   private Demo                        public static Demo createObj                  if obj    null                   obj   new Demo                              return obj                   Demo obj1   Demo createObj      Here  Only 1 instance will be alive at a time

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Static method example  class StaticDemo     public static void copyArg String str1  String str2               str2   str1         System out println  First String arg is    str1          System out println  Second String arg is    str2             public static void main String agrs                  StaticDemo copyArg  XYZ    ABC          copyArg  XYZ    ABC              Output   First String arg is  XYZ  Second String arg is  XYZ   As you can see in the above example that for calling static method  I didn   t even use an object  It can be directly called in a program or by using class name   Non-static method example  class Test       public void display                System out println  I m non-static method              public static void main String agrs                 Test obj new Test           obj display              Output   I m non-static method   A non-static method is always be called by using the object of class as shown in the above example   Key Points   How to call static methods  direct or using class name   StaticDemo copyArg s1  s2     or  copyArg s1  s2     How to call a non-static method  using object of the class   Test obj   new Test

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- First we must know that the diff bet static and non static methods  is differ from static and non static variables     - this code explain static method - non static method and what is the diff       public class MyClass           static               System out println  this is static routine                              public static void foo                System out println  this is static method                        public void blabla              System out println  this is non static method                        public static void main String   args                                                                                                               1- in static method you can implement the method inside its class like                           you don t have to make an object of this class to implement this method                         MyClass foo                this is correct                                                     MyClass blabla             this is not correct because any non static                     method you must make an object from the class to access it like this                                  MyClass m   new MyClass                                                                        m blabla                                                                                                                                                                                   access static method without make an object              MyClass foo                 MyClass m   new MyClass                   access non static method via make object              m blabla                                  access static method make a warning but the code run ok                 because you don t have to make an object from MyClass                 you can easily call it MyClass foo                                m foo                               output of the code               this is static routine          this is static method      this is non static method      this is static method          - this code explain static method - non static Variables and what is the diff         public class Myclass2                       you can declare static variable here                       or you can write  int callCount   0                      make the same thing                    static int callCount   0    int callCount   0                  static int callCount   0                       public void method                                                                                                                     Can i declare a static variable inside static member function in Java                      - no you can t                      static int callCount   0      error                                                                                                                                                                    static variable                    callCount                    System out println  Calls in method  1        callCount                                      public void method2                     int callCount2   0                       non static variable                       callCount2                    System out println  Calls in method  2        callCount2                                   public static void main String   args                 Myclass2 m   new Myclass2                    method  1  calls                 m method                  m method                 m method                    method  2  calls                 m method2                 m method2                 m method2                                        output              Calls in method  1    1            Calls in method  1    2            Calls in method  1    3            Calls in method  2    1            Calls in method  2    1            Calls in method  2    1

[java] What is the difference between a static method and a non-static method?

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