What is static method

I can not understand how to use static method
What is the difference between
int a;
static int a;
what is the meaning of static??

I would add that a static member exists for the class independently of any instances of the class.
This means that you can refer to it at any time by using TheClass.theMember.
This applies to the methods too, like TheClass.theMethod().

Similar Messages

What a static method cannot be overriden?

Parent class
public class Person {
   private String surname;
   private String firstName;
   private String secondName;
   public Person(String surname,
                 String firstName,
                 String secondName) {
        this.surname = surname;
        this.firstName = firstName;
        this.secondName = secondName;
   public static void test() { ; }
}Sub class
public class Member extends Person {
     private int membershipNumber;
                 public Member(String surname,
                  String firstName,
                  String secondName,
                  int membershipNumber) {
          super(surname, firstName, secondName);
          this.membershipNumber = membershipNumber;
     public String toString() {
          return membershipNumber + "-" + super.toString();
     public void test() { System.out.println("test") ; }
}And I got compilation error :
H:\java\wshp2>javac *.java
Member.java:20: test() in Member cannot override test() in Person; overridden me
thod is static
public void test() { System.out.println("test") ; }
^
1 error
H:\java\wshp2>pause
Since static method and the overriding method are going to be used differently (in different ways), why it can't be allowed?
Static method is a Class method whereas the overriding method is a instance method, they can be distinguished. What is the reason behind this?
Please enlighten me.
Thanks

Are final method bound at compile-time?Basically when a method is "bound" cannot be used to explain the behaviour of methods in Java. It's the other way around. It's the characteristics of a method that decides when it can be "bound". But that's an implementation issue and not part of the language itself.
A static method cannot be overriden because it's not meant to be overridden. It's against the semantics of a static method to be overridden. Also if you declare a method final you decide that you don't want it to be overriden. In both cases, based on this non-overriding restriction, the compiler can decide when to "bind" the method.

Static methods, what for?

What are static methods for? is there something that is not possible through methods associated with instances (non-static methods) ?

There are many examples of static mehods in the Java API. For example the Math or the System class. All methods in this classes are static. So you dont have to instantiate the system class. In fact it is even not possible to instantiate the System class. System is final and all Constructors are private.
Another use for static methods is the access to private static variables.

Static Methods, the case of HashMap

    static int hash(Object x) {
        int h = x.hashCode();
        h += ~(h << 9);
        h ^= (h >>> 14);
        h += (h << 4);
        h ^= (h >>> 10);
        return h;I was cruising the HashMap class. And I noticed right away that all non interface methods were static package methods. Now isn't that bad OOP practice? Right. It breaks the inheritance relationship.
It means I cannot make a subclass of HashMap and re-write that hash function. Was that intentional?
on a OOP perspective or
on a down to earth matter,
Are static method more performant in speed? Or memory ( i guess yes here)? or what?

I was cruising the HashMap class. And I noticed right
away that all non interface methods were static
package methods. Now isn't that bad OOP practice?
Right. It breaks the inheritance relationship.
It means I cannot make a subclass of HashMap and
re-write that hash function. Was that intentional?If they are package-private, I take it for granted they didn't want application developers to redefine these methods.
If they are static, they are also preventing themselves (Javasoft) to override them in subclasses that would be included in the JDK.
I'd say in both cases, that it is intentional, since, at least in the case of the hash function, the intent is to disperse hash results even for low-dispersing custom hash functions, as was explained in another thread in ALT (wasn't it you already? ;-).
This is maybe questionable, but defendable, that they didn't want any subclass to mess with these "optimizations".
You can regard this as poor OO practice, but this is no more hampering you that if they had declared the method as private.
I acknowledge that declaring the method private has the advantage of making explicit that they don't want anyone to override it.
But by declaring it static package, they ensure no-one can override it, so the other methods in HashMap relying on this method are guaranteed that no subclass can mess with it, but other classes in the same package (say, WeakHashMap, HashSet,...), can call it. all the same
Are static method more performant in speed? Or memory
( i guess yes here)? or what?Static methods are not faster in themselves, but invoking them may be, since they can be "statically" resolved.
When the calling class is loaded in memory, the callee is loaded too, and the interpreter or JIT or HotSpot is free to inline the static method's body (no indirection).
Even if it doesn't, invoking the static method implies to moving the program counter or pointer, or whatever, to an adress that has already been resolved once and for all (one indirection),
whereas invoking a virtual method implies a double indirection, looking up the address in some kind of dynamic table (one per class, determined by the target object's leaf class).
There are indeed two different bytecodes for these two situations!

What's wrong with static methods?

Answers on an postcard please.

I think the point here is that sometimes people come from a procedural background (or maybe no background) and they start with main, and one static method leads to another. They reach a tipping point where they are reluctant to define non-static methods to a class because it's all static elsewhere. And static method can't access instance data, so their data becomes largely static as well. When the dust settles, they are programming procedually in Java. So too many static methods is a sign that you may be programming procedurally instead of doing OOP, but using static appropriately is still cool.
And let's not get pedantic. What goes wrong if I make my String class's getLength method static?
public final class MyString {
    private int length;
    public static int getLength(String s) {
        return s.length;
}It's a misuse of static, but it doesn't break my design.

What is the use of private static method/variable?

Hi All,
I have read lots of books and tried lots of things but still not very clear on the
topic above.
When exactly do we HAVE to use private static methods?
private implies its only for class, cannot be accessed outside.
But then static means, it can be accessed giving classname.method.
They seem to be contradicting each other.
Any examples explaining the exact behaviour will be well appreciated.
Thanks,
Chandra Mohan

Static doesn't really "mean" that the method/field is intended for use outside the class - that is exactly what the access modifier is for.
Static implies that it is for use in relation to the class itself, as opposed to an instance of the class.
One good example of a private static method would be a utility method that is (only) invoked by other (possibly public) static methods; it is not required outside the class (indeed, it might be dangerous to expose the method) but it must be called from another static method so it, in turn, must be static.
Hope this helps.

What 's the advantage of static method.

I think if a method is declared as static, the program should allocate some spaces for the method when the program start. However, I found many static method in an erp open source project. What make me confused is that it will cost many spaces.
Perhaps they want to lose some spaces for speed???
Can somebody answer my question.thanks!

> I think if a method is declared as static, the
program should allocate some spaces for the method
when the program start. However, I found many static
method in an erp open source project. What make me
confused is that it will cost many spaces.
Perhaps they want to lose some spaces for speed???
Can somebody answer my question.thanks!
To be sincere, I've never thought about performance cost when static methods are used. I decide to create and use them mainly whether I have the "feeling" that it will provide me benefits, in terms of designing. Yes, it's like a feeling. I am not able to explain you why or how I have this feeling, I'm not native in English language, so choosing the appropriate words to explain my ideas sometimes is hard to me. Besides. I admit that I am a little bit lazy in this moment, I don't want to search through some dictionary...;-).
I think the more you develop your abilities and skills in java programming, the more you can feel, you can have this "feeling", and naturally you figure out in which situations using static methods is a better choice.

What is the purpose of Static methods inside a class?

Hi,
What is the purpose of Static methods inside a class?
I want the answers apart from "A static method does not require instance of class(to access) and it can directly be accessed by the class name itself"
My question is what is the exact purpose of a static method ?
Unlike attributes, a separate copy of instance attributes will be created for each instance of a class where as only one copy of static attributes will be created for all instances.
Will a separate copy of instance method be created for each instance of a class and only one copy of static methods be create?
Points will be rewarded for all helpful answers.

Hi Sharma,
Static methods is used to access statics attributes of a class. We use static attributes when we want to share the same attribute with all instances of a class, in this case if you chage this attribute through the instance A this change will change will be reflected in instance B, C........etc.
I think that your question is correct -> a separate copy of instance method will be created for each instance of a class and only one copy of static methods be create ?
"A static method does not require instance of class(to access) and it can directly be accessed by the class name itself"
Static Method: call method class=>method.
Instance Method: call method instance->method.
Take a look at this wiki pages.
[https://wiki.sdn.sap.com/wiki/x/o5k]
[https://wiki.sdn.sap.com/wiki/x/ZtM]
Best regards.
Marcelo Ramos

What's the differences between a singleton and a class with static methods

Hi everybody.
My question is in the subject. Perhaps "differences" is not the good word. The positive and negative points ?
Imagine you have to write a connection pool, sure you gonna choose a singleton but why ?
Thank you very much.

A class is a class. Java doesn't have (and I wish it
did) a static outer class. Any class can extend
another class or implement an interface.A Class object cannot extend or implement anything - it is not under programmer control in any way. You can create a class which implements interfaces, but calling static methods is completely unrelated. Interfaces only affect instance methods, not class ones. I think all of your comparison to C++ is actually confusing you more. In Java, there is a real class object at runtime, as opposed to C++.
YATArchivist makes a good point about being able to
serialize, altho I've not met that desire in practice.
Maybe a concrete example would help.
mattbunch makes another point that I don't understand.
A class can implement an interface whether it sticks
its data in statics or in a dobject, so I guess I
still don't get that one.See my comment above. Static methods are free from all contractual obligations.
I prefer instance singletons to singleton classes because they are more flexible to change. For instance I created a thread pool singleton which worked by passing the instance around, but later I needed two thread pools so I made a slight modification to the class and poof! no more singleton and 99% of my code compiled cleanly against it.
When possible, I prefer to hand the instance off from object to object rather than have everything call Singleton.instance() since it makes changes like I mentioned earlier more feasible.

Using a non-static vector in a generic class with static methods

I have a little problem with a class (the code is shown underneath). The problem is the Assign method. This method should return a clone (an exact copy) of the set given as an argument. When making a new instance of a GenericSet (with the Initialize method) within the Assign method, the variables of the original set and the clone have both a reference to the same vector, while there exists two instances of GenericSet. My question is how to refer the clone GenericSet's argument to a new vector instead of the existing vector of the original GenericSet. I hope you can help me. Thanks
package genericset;
import java.util.*;
public class GenericSet<E>{
private Vector v;
public GenericSet(Vector vec) {
v = vec;
private <T extends Comparable> Item<T> get(int index) {
return (Item<T>) v.get(index);
public static <T extends Comparable> GenericSet<T> initialize() {
return new GenericSet<T>(new Vector());
public Vector getVector() {
return v;
public static <T extends Comparable> GenericSet<T> insert (GenericSet<T> z, Item<T> i){
GenericSet<T> g = assign(z);
Vector v = g.getVector();
if (!member(g,i))
v.addElement(i);
return g;
public static <T extends Comparable> GenericSet<T> delete(GenericSet<T> z, Item<T> i){
GenericSet<T> g = assign(z);
Vector v = g.getVector();
if (member(g,i))
v.remove(i);
return g;
public static <T extends Comparable> boolean member(GenericSet<T> z, Item<T> i) {
Vector v = z.getVector();
return v.contains(i);
public static <T extends Comparable> boolean equal(GenericSet<T> z1, GenericSet<T> z2) {
Vector v1 = z1.getVector();
Vector v2 = z2.getVector();
if((v1 == null) && (v2 != null))
return false;
return v1.equals(v2);
public static <T extends Comparable> boolean empty(GenericSet<T> z) {
return (cardinality(z) == 0);
public static <T extends Comparable> GenericSet<T> union(GenericSet<T> z1, GenericSet<T> z2) {
GenericSet<T> g = assign(z1);
for(int i=0; i<cardinality(z2); i++) {
Item<T> elem = z2.get(i);
insert(g, elem);
return g;
public static <T extends Comparable> GenericSet<T> intersection(GenericSet<T> z1, GenericSet<T> z2) {
GenericSet<T> g = initialize();
for(int i=0; i<cardinality(z2); i++) {
Item<T> elem = z2.get(i);
if(member(z1, elem))
insert(g, elem);
return g;
public static <T extends Comparable> GenericSet<T> difference(GenericSet<T> z1, GenericSet<T> z2) {
GenericSet<T> g = initialize();
for(int i=0; i<cardinality(z1); i++) {
Item<T> elem = z1.get(i);
if(!member(z2, elem))
insert(g, elem);
for(int i=0; i<cardinality(z2); i++) {
Item<T> elem = z2.get(i);
if(!member(z1, elem))
insert(g, elem);
return g;
public static <T extends Comparable> GenericSet<T> assign(GenericSet<T> z) {
GenericSet<T> g = initialize();
for(int i=0; i<cardinality(z); i++) {
Item<T> elem = z.get(i);
insert(g, elem);
return g;
public static <T extends Comparable> boolean subset(GenericSet<T> z1, GenericSet<T> z2) {
for(int i=0; i<cardinality(z1); i++) {
Item<T> elem = z1.get(i);
if(!member(z2, elem))
return false;
return true;
public static <T extends Comparable> int cardinality(GenericSet<T> z){
Vector v = z.getVector();
return v.size();
}

The issue is not "reference a non-static interface", but simply that you cannot reference a non-static field in a static method - what value of the field ed would the static method use? Seems to me your findEditorData should look something like this:   public static EditorBean findEditorData( String username, EditorBean editorData )
      return editorData.ed.findEditor( username );
   }

Using HttpServletRequest object to share variables between static methods.

Does anyone know of the overhead/performance implications of using the HttpServletRequest object to share variables between a static method and the calling code?
First, let me explain why I am doing it.
I have some pagination code that I would like to share across multiple servlets. So I pulled the pagination code out, and created a static method that these servlets could all use for their pagination.
public class Pagination {
     public static void setPagination (HttpServletRequest request, Config conf, int totalRows) {
          int page = 0;
          if (request.getParameter("page") != null) {
               page = new Integer(request.getParameter("page")).intValue();
          int articlesPerPage = conf.getArticlesPerPage();
          int pageBoundary = conf.getPageBoundary();
            int numOfPages = totalRows / articlesPerPage;
            // Checks if the page variable is empty (not set)
            if (page == 0 || (page > numOfPages && (totalRows % articlesPerPage) == 0 && page < numOfPages + 1)) {
             page = 1; // If it is empty, we're on page 1
          // Ex: (2 * 25) - 25 = 25 <- data starts at 25
         int startRow = page * articlesPerPage - (articlesPerPage);
         int endRow = startRow + (articlesPerPage);
         // Set array of page numbers.
         int minDisplayPage = page - pageBoundary;
         if (minDisplayPage < 1) {
              minDisplayPage = 1;
         int maxDisplayPage = page + pageBoundary;
         if (maxDisplayPage > numOfPages) {
              maxDisplayPage = numOfPages;
         int arraySize = (maxDisplayPage - minDisplayPage) + 1;
         // Check if there is a remainder page (partially filled page).
         if ((totalRows % articlesPerPage) != 0) arraySize++;
         // Set array to correct size.
         int[] pages = new int[arraySize];
         // Fill the array.
         for (int i = 1; i <= pages.length; i++) {
              pages[i - 1] = i;
         // Set pageNext and pagePrev variables.
         if (page != 1) {
              int pagePrev = page - 1;
              request.setAttribute("pagePrev", pagePrev);
         if ((totalRows - (articlesPerPage * page)) > 0) {
             int pageNext = page + 1;
             request.setAttribute("pageNext", pageNext);
         // These will be used by calling code for SQL query.
         request.setAttribute("startRow", startRow);
         request.setAttribute("endRow", endRow);
         // These will be used in JSP page.
         request.setAttribute("totalRows", totalRows);
         request.setAttribute("numOfPages", numOfPages);
         request.setAttribute("page", page);
         request.setAttribute("pages", pages);
}I need two parameters from this method (startrow and endrow) so I can perform my SQL queries. Since this is a multithreaded app, I do not want to use class variables that I will later retrieve through methods.
So my solution was to just set the two parameters in the request and grab them later with the calling code like this:
// Set pagination
Pagination.setPagination(request, conf, tl.getTotalRows());
// Grab variables set into request by static method
int startRow = new Integer(request.getAttribute("startRow").toString());
int endRow = new Integer(request.getAttribute("endRow").toString());
// Use startRow and endRow for SQL query below...Does anyone see any problem with this from a resource/performance standpoint? Any idea on what the overhead is in using the HttpServletRequest object like this to pass variables around?
Thanks for any thoughts.

You could either
- create instance vars in both controllers and set them accordingly to point to the same object (from the App Delegate) OR
- create an instance variable on the App Delegate and access it from within the view controllers
Hope this helps!

Can you set a global EntityResolver (via system property, or static method)

I'm trying to set a customized EntityResolver (telling the xml parser where to look for XML schema files).
Usually, you'd use the standard syntax - somehting like:
SaxParser parser=new SaxParser();
parser.parser.setEntityResolver(myResolver);
However, I was wondering whether you can set a "global" EntityResolver, to be used as default for all parsers ?
Maybe this can be done through some system property, or a static method somewhere in the parsing XML ?
(BTW, I need it because I'm using some third-party API, that encapsulates a SaxParser, but won't let me access it, so I can't configure it directly).
thanks.

I don't think you can.
What is possible is to set content on the folder resource itself; that would be returned instead of the page you mentioned.

How to call a static method in a class if I have just the object?

Hello. I have an abstract class A where I have a static method blah(). I have 2 classes that extend class A called B and C. In both classes I override method blah(). I have an array with objects of type B and C.
For every instance object of the array, I'm trying to call the static method in the corresponding class. For objects of type B I want to call blah() method in B class and for objects of type C I want to call blah() method in C class. I know it's possible to call a static method with the name of the object, too, but for some reason (?) it calls blah() method in class A if I try this.
So my question is: how do I code this? I guess I need to cast to the class name and then call the method with the class name, but I couldn't do it. I tried to use getClass() method to get the class name and it works, but I didn't know what to do from here...
So any help would be appreciated. Thank you.

As somebody already said, to get the behavior you
want, make the methods non-static.You all asked me why I need that method to be
static... I'm not surprised to hear this question
because I asked all my friends before posting here,
and all of them asked me this... It's because some
complicated reasons, I doubt it.
the application I'm writing is
quite big...Irrelevant.
Umm... So what you're saying is there is no way to do
this with that method being static? The behavior you describe cannot be obtained with only static methods in Java. You'd have to explicitly determine the class and then explicitly call the correct class' method.

Calling a non-static method from another Class

Hello forum experts:
Please excuse me for my poor Java vocabulary. I am a newbie and requesting for help. So please bear with me! I am listing below the program flow to enable the experts understand the problem and guide me towards a solution.
1. ClassA instantiates ClassB to create an object instance, say ObjB1 that
    populates a JTable.
2. User selects a row in the table and then clicks a button on the icon toolbar
    which is part of UIMenu class.
3. This user action is to invoke a method UpdateDatabase() of object ObjB1. Now I want to call this method from UIMenu class.
(a). I could create a new instance ObjB2 of ClassB and call UpdateDatabase(),
                                  == OR ==
(b). I could declare UpdateDatabase() as static and call this method without
     creating a new instance of ClassB.With option (a), I will be looking at two different object instances.The UpdateDatabase() method manipulates
object specific data.
With option (b), if I declare the method as static, the variables used in the method would also have to be static.
The variables, in which case, would not be object specific.
Is there a way or technique in Java that will allow me to reference the UpdateDatabase() method of the existing
object ObjB1 without requiring me to use static variables? In other words, call non-static methods in a static
way?
Any ideas or thoughts will be of tremendous help. Thanks in advance.

Hello Forum:
Danny_From_Tower, Encephalatic: Thank you both for your responses.
Here is what I have done so far. I have a button called "btnAccept" created in the class MyMenu.
and declared as public.
public class MyMenu {
    public JButton btnAccept;
     //Constructor
     public MyMenu()     {
          btnAccept = new JButton("Accept");
}     I instantiate an object for MyMenu class in the main application class MyApp.
public class MyApp {
     private     MyMenu menu;
     //Constructor
     public MyApp(){
          menu = new MyMenu();
     public void openOrder(){
           MyGUI MyIntFrame = new MyGUI(menu.btnAccept);
}I pass this button all the way down to the class detail02. Now I want to set up a listener for this
button in the class detail02. I am not able to do this.
public class MyGUI {
     private JButton acceptButton;
     private detail02 dtl1 = new detail02(acceptButton);
     //Constructor
     public AppGUI(JButton iButton){
     acceptButton = iButton;
public class detail02{
    private JButton acceptButton;
    //Constructor
    public detail02(JButton iButton){
      acceptButton = iButton;
      acceptButton.addActionListener(new acceptListener());
   //method
    private void acceptListener_actionPerformed(ActionEvent e){
       System.out.println("Menu item [" + e.getActionCommand( ) + "] was pressed.");
    class acceptListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
               acceptListener_actionPerformed(e);
} I am not able to get the button Listener to work. I get NullPointerException at this line
          acceptButton.addActionListener(new acceptListener());in the class detail02.
Is this the right way? Or is there a better way of accomplishing my objective?
Please help. Your inputs are precious! Thank you very much for your time!

Calling a static method from another class

public class Command
    public static void sortCommands(String command, String order, List object)
         if(command.equalsIgnoreCase("merge") && order == "a")
              object.setAscending(true);
              Mergesort.mergesort(object.list);                  // line 85
}and
public class Mergesort
     public static void mergesort (int[] a)
          mergesort(a, 0, a.length-1);
     private static void mergesort (int[] a, int l, int r)
     private static void merge (int[] a, int l, int m, int r)
}Error:
Command.java:85: cannot find symbol
symbol : variable Mergesort
location: class Command
Mergesort.mergesort(object.list)
What am I doing wrong here? Within the Command class I am calling mergesort(), a static method, from a static method. I use the dot operator + object so that the compiler would recognize the 'list' array. I tried using the
Mergesort.mergesort(object.list);notation in hopes that it would work like this:
Class.staticMethod(parameters);but either I am mistaken, misunderstood the documentation or both. Mergesort is not a variable. Any help would be appreciated, I have been hitting a brick wall for hours with Java documentation. Thanks all.

[Javapedia: Classpath|http://wiki.java.net/bin/view/Javapedia/ClassPath]
[How Classes are Found|http://java.sun.com/j2se/1.5.0/docs/tooldocs/findingclasses.html]
[Setting the class path (Windows)|http://java.sun.com/j2se/1.5.0/docs/tooldocs/windows/classpath.html]
[Setting the class path (Solaris/Linux)|http://java.sun.com/j2se/1.5.0/docs/tooldocs/solaris/classpath.html]
[Understanding the Java ClassLoader|http://www-106.ibm.com/developerworks/edu/j-dw-javaclass-i.html]
java -cp .;<any other directories or jars> YourClassNameYou get a NoClassDefFoundError message because the JVM (Java Virtual Machine) can't find your class. The way to remedy this is to ensure that your class is included in the classpath. The example assumes that you are in the same directory as the class you're trying to run.
javac -classpath .;<any additional jar files or directories> YourClassName.javaYou get a "cannot resolve symbol" message because the compiler can't find your class. The way to remedy this is to ensure that your class is included in the classpath. The example assumes that you are in the same directory as the class you're trying to run.

What is static method

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