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Why can’t static methods be abstract in Java?
  • Last Updated : 08 May, 2020

In Java, a static method cannot be abstract. Doing so will cause compilation errors.

Example:




// Java program to demonstrate
// abstract static method
  
import java.io.*;
  
// super-class A
abstract class A {
  
    // abstract static method func
    // it has no body
    abstract static void func();
}
  
// subclass class B
class B extends A {
  
    // class B must override func() method
    static void func()
    {
        System.out.println(
            "Static abstract"
            + " method implemented.");
    }
}
  
// Driver class
public class Demo {
    public static void main(String args[])
    {
  
        // Calling the abstract
        // static method func()
        B.func();
    }
}

The above code is incorrect as static methods cannot be abstract. When run, the Compilation Error that occurs is:

Compilation Error:

prog.java:12: error: illegal combination of modifiers: abstract and static
    abstract static void func();
                         ^
1 error

What will happen if a static method is made abstract?



Assuming we make a static method abstract. Then that method will be written as:

public abstract static void func();
  • Scenario 1: When a method is described as abstract by using the abstract type modifier, it becomes responsibility of the subclass to implement it because they have no specified implementation in the super-class. Thus, a subclass must override them to provide method definition.

  • Scenario 2: Now when a method is described as static, it makes it clear that this static method cannot be overridden by any subclass (It makes the static method hidden) as static members are compile-time elements and overriding them will make it runtime elements (Runtime Polymorphism).

Now considering Scenario 1, if the func method is described as abstract, it must have a definition in the subclass. But according to Scenario 2, the static func method cannot be overridden in any subclass and hence it cannot have a definition then. So the scenarios seem to contradict each other. Hence our assumption for static func method to be abstract fails. Therfore, a static method cannot be abstract.

Then that method will be coded as:

public static void func();

Example:




// Java program to demonstrate
// abstract static method
  
import java.io.*;
  
// super-class A
abstract class A {
  
    // static method func
    static void func()
    {
        System.out.println(
            "Static method implemented.");
    }
  
    // abstract method func1
    // it has no body
    abstract void func1();
}
  
// subclass class B
class B extends A {
  
    // class B must override func1() method
    void func1()
    {
        System.out.println(
            "Abstract method implemented.");
    }
}
  
// Driver class
public class Demo {
    public static void main(String args[])
    {
  
        // Calling the abstract
        // static method func()
        B.func();
        B b = new B();
        b.func1();
    }
}
Output:
Static method implemented.
Abstract method implemented.

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