Static Classes In Java

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Is there anything like static class in java?

What is the meaning of such a class. Do all the methods of the static class need to be static too?

Is it required the other way round, that if a class contains all the static methods, shall the class be static too?

What are static classes good for?

Static class in Java, A static inner class is a nested class which is a static member of the outer class. It can be accessed without instantiating the outer class, using  Java 8 Object Oriented Programming Programming. You cannot use the static keyword with a class unless it is an inner class. A static inner class is a nested class which is a static member of the outer class. It can be accessed without instantiating the outer class, using other static members. Just like static members, a static nested class does not have access to the instance variables and methods of the outer class.

Well, Java has "static nested classes", but they're not at all the same as C#'s static classes, if that's where you were coming from. A static nested class is just one which doesn't implicitly have a reference to an instance of the outer class.

Static nested classes can have instance methods and static methods.

There's no such thing as a top-level static class in Java.

What is a static class in Java?, Java has static nested classes but it sounds like you're looking for a top-level static class. Java has no way of making a top-level class static but you can simulate  Static classes are basically a way of grouping classes together in Java. Java doesn't allow you to create top-level static classes; only nested (inner) static classes. Let's take a look at an example. Here's a class called CarParts that declares a static inner class called Wheel.

There is a static nested class, this [static nested] class does not need an instance of the enclosing class in order to be instantiated itself.

These classes [static nested ones] can access only the static members of the enclosing class [since it does not have any reference to instances of the enclosing class...]

code sample:

public class Test { 
  class A { } 
  static class B { }
  public static void main(String[] args) { 
    /*will fail - compilation error, you need an instance of Test to instantiate A*/
    A a = new A(); 
    /*will compile successfully, not instance of Test is needed to instantiate B */
    B b = new B(); 
  }
}

Static Classes In Java, Static keyword can be used with class, variable, method and block. Static members belong to the class instead of a specific instance, this means if you make a  Java has no way of making a top-level class static but you can simulate a static class like this: Declare your class final - Prevents extension of the class since extending a static class makes no sense Make the constructor private - Prevents instantiation by client code as it makes no sense to instantiate a static class

Yes there is a static nested class in java. When you declare a nested class static, it automatically becomes a stand alone class which can be instantiated without having to instantiate the outer class it belongs to.

Example:

public class A
{

 public static class B
 {
 }
}

Because class B is declared static you can explicitly instantiate as:

B b = new B();

Note if class B wasn't declared static to make it stand alone, an instance object call would've looked like this:

A a= new A();
B b = a.new B();

Java, Static classes are basically a way of grouping classes together in Java. Java doesn't allow you to create top-level static classes; only nested (inner) static classes  Java Static Class: A step further in your Java programming journey Classes in Java. Java is an object oriented language. A class in Java is just a collection of objects. It is a universal Nested Classes. Java supports the concept of Nested Classes. Nested Classes are classes that can be defined

What's happening when a members inside a class is declared as static..? That members can be accessed without instantiating the class. Therefore making outer class(top level class) static has no meaning. Therefore it is not allowed.

But you can set inner classes as static (As it is a member of the top level class). Then that class can be accessed without instantiating the top level class. Consider the following example.

public class A {
    public static class B {

    }
}

Now, inside a different class C, class B can be accessed without making an instance of class A.

public class C {
    A.B ab = new A.B();
}

static classes can have non-static members too. Only the class gets static.

But if the static keyword is removed from class B, it cannot be accessed directly without making an instance of A.

public class C {
    A a = new A();
    A.B ab = a. new B();
}

But we cannot have static members inside a non-static inner class.

Java Static Class: A Tutorial on Static Classes in Java, In Java, if a field is declared static, then exactly a single copy of that field is created and shared among all instances of that class. It doesn't  In Java, static is a keyword used to describe how objects are managed in memory. It means that the static object belongs specifically to the class, instead of instances of that class. Variables,

A Guide to the Static Keyword in Java, Static nested classes do not have access to other members of the enclosing class​. As a member of the OuterClass , a nested class can be declared private , public​  In the Java programming language, the keyword static indicates that the particular member belongs to a type itself, rather than to an instance of that type. This means that only one instance of that static member is created which is shared across all instances of the class. The keyword can be applied to variables, methods, blocks and nested class.

Nested Classes (The Java™ Tutorials > Learning the Java , In Java, nested classes are categorized as either static member classes or inner classes. Inner classes are non-static member classes, local  A static class i.e. created inside a class is called static nested class in java. It cannot access non-static data members and methods. It can be accessed by outer class name. It can access static data members of outer class including private. Static nested class cannot access non-static (instance) data member or method. Java static nested class example with instance method

Static classes and inner classes in Java, In Java, static nested classes are associated with the outer class. This is why static nested classes can only access the class members (static fields and methods)  In Java, a static member is a member of a class that isn’t associated with an instance of a class. Instead, the member belongs to the class itself. As a result, you can access the static member without first creating a class instance. The two types of static members are static fields and static methods:

Comments
  • You might be interested in stackoverflow.com/questions/3584113/java-static-class
  • Static classes are basically used to grouping classes together.
  • a class Foo with only static methods is not the same as static class Foo
  • @Evorlor: If a class is declared final then its methods are automatically (effectively) final. This is because a final class cannot be subclassed, and thus its methods cannot be overridden (i.e., are effectively final). docs.oracle.com/javase/tutorial/java/IandI/final.html
  • This answer maybe addresses what the OP meant, but it (currently) does not explain Java static classes, and so does not answer the question at all! This is very bad for people who get here trying to figure out what a static class means in Java.
  • @JBoy: There is such a thing as "static class" in Java, which is what the question is about, but this answer does not at all explain. Instead, it explains how to simulate in Java what the answer calls a "static class" - but which is not what a "static class" in Java is! (Maybe it's what's called a "static class" in some other language(s), but people coming here to learn about Java static classes will be misled and confused.)
  • you should explicitly mention that private MyStaticClass () { // private constructor myStaticMember = 1; } will have NO effect at all since the constructor will not be called. But this is not the point. I am still very confused about the utility of static inner classes in Java and their utility or added value.
  • In Java Why does static nested class allow instance methods? What is the use of a instance method in such a class?
  • @Geek: Did you read my answer? Read the second sentence carefully. Why would you not want to be able to have instance methods of static classes? You can create instances of them, after all.
  • @Geek: Yes, it's entirely permissable. Your "understanding" that static classes are utility classes is incorrect, basically. That's not what static classes in Java mean at all.
  • @Geek: Yes. Exactly as I wrote in my answer: "A static nested class is just one which doesn't implicitly have a reference to an instance of the outer class."
  • @KhurramAli: Do you mean implicitly? They're certainly not explicitly static, given that you don't use the keyword static when declaring them. They're implicitly static in that you don't need a reference to anything else in order to construct one. Personally I find the static/non-static terminology a bit odd for nested classes anyway... I think it would be simpler to talk about what the behaviour is.