This java.lang.AbstractMethodError is usually thrown when we try to invoke the abstract method.

AbstractMethodError:

This java.lang.AbstractMethodError is usually thrown when we try to invoke the abstract method.

we know that an abstract method cannot be invoked and if we try to do so then you will get a compile-time error.So you may think how this error is thrown at run-time?.

The reason is binary incompatibility-what does it mean?

Whenever a class is modified,other classes that refer to this (modified) class will not be aware of the changes made in it.So all the classes must be compiled as a whole.If not then you may encounter one of the subclasses of incompatible class change error.
“This error indicates that the method that you invoke is converted into an abstract method now”.

see the following example to have an idea about this error

class B
{
public void display()
{
System.out.println(“I am inside B”);
}
}

import java.util.*;
public class A extends B
{
public static void main(String args[])
{
A a=new A();
a.display();
}
}

output:

C:\blog>javac A.java

C:\blog>java A
I am inside B

Now i am going to convert the display() method as an abstract method and compile it alone.

abstract class B
{
public abstract void display();
}

Output:

C:\blog>javac A.java

C:\blog>java A
I am inside B

C:\blog>javac B.java

C:\blog>java A
Exception in thread “main” java.lang.AbstractMethodError: B.display()V
at A.display(A.java:3)
at A.main(A.java:8)

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