How to Resolve a java.lang.AbstractMethodError in Java?

Sometimes, programmers encounter AbstractMethodError in Java at the software's runtime. If you, too, don’t know about this error, Tutorials24x7 has got a solution for you!

In this tutorial, we will discuss what AbstractMethodError is, learn when it may happen and know how we can resolve the issue.

What is a java.lang.AbstractMethodError in Java?

The java.lang.AbstractMethodError is a runtime error in the Java programming language. It happens when the class lacks the implementation of abstract method(s) in one of its interfaces or abstract parent class. The compiler catches the error and signifies a mismatch between the expected and actual class hierarchy.

The following code syntax gets you the AbstractMethodError:

public interface MyInterface {
   void myMethod();
}
public class MyClass implements MyInterface {
   // Missing implementation of myMethod.
}

How can we resolve AbstractMethodError in Java?

The java.lang.AbstractMethodError happens when a class attempts to invoke an abstract method that has not been implemented by any subclass before. You must write the following program to resolve AbstractMethodError in Java:

interface MyAbstractClass {
   void myMethod();
}
// Class implements the interface and provides the implementation.
class MyClass implements MyAbstractClass {
   // It will implement the abstract method.
   public void myMethod() {
       System.out.println("myMethod is implemented.");
   }
   public static void main(String[] args) {
       // It creates an instance of MyClass.
       MyClass obj = new MyClass();
       
       // Calls the implemented method.
       obj.myMethod();
   }
}

Output:

myMethod is implemented.

Explanation:

Here is a step-by-step explanation of the above program:

1. First, we defined an interface MyAbstractClass with the abstract method myMethod(). 
2. We create a class, MyClass, that implements the MyAbstractClass interface. Hence, it provides an implementation for myMethod() method.
3. Next, Inside the myMethod() implementation we print the message “myMethod is implemented.” for better understanding.
4. In the main() method, we have written code to create an object obj of MyClass class.
5. Next, we call the myMethod() method on the obj object. The code invokes the implemented method in MyClass class.
6. At last, when you execute the program, it will run successfully, and it prints the message “myMethod is implemented.'' to the console.

Summary

To resolve java.lang.AbstractMethodError, you should carefully check the interface methods the class implements and ensure all necessary methods are correctly defined. You should also check the method signatures in both the interface and implementing classes to ensure they match exactly, including return types and parameters.

Ensuring that your project’s dependencies are correctly managed and there are no conflicts between different versions of libraries that may contain conflicting implementations will also help.