Two different Java objects are always equal regardless of fields value

I have classes defined like below:

@Data
@NoArgsConstructor
@AllArgsConstructor
@SuperBuilder

public abstract class A {
    private Enum myEnum;
}

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@SuperBuilder

public class KA extends A {
    private MyPackage pck;
    private String field1;
    private String field2;
}

I tested them with the following code:

KA ka1 = new KA();
KA ka2 = new KA();
System.out.println("Object equal: " + ka1.equals(ka2));

For KA, either no-arg constructor or constructor with totally different arguments, I would get they are equal.

I want KA to be using the default equal method of Object class which is comparing the object memory addresses.

What is wrong here?

Assuming that you're using lombok's @Data, it generates an .equals() method for your class based on the fields within the annotated class. I.e. the equals-method does not include the fields of the child class. Read the documentation of the annotation here: https://projectlombok.org/features/Data

Class KA inherits its equals method from A, which uses a field-based equality due to @Data. Specifically, it returns true if the two instances have the same value for myEnum and are exactly the same class.

In order to get the same identity-based equality behavior matching Object.equals, you'll need to override the equality methods in KA to have the desired behavior:

public class KA extends A {
    private MyPackage pck;
    private String field1;
    private String field2;

    @Override
    public boolean equals(Object o) {
        return this == o;
    }

    @Override
    public int hashCode() {
        return System.identityHashCode(this);
    }
}

Note that this will satisfy the equivalence relation required by equals. Lombok's equals implementation is careful to ensure that objects of different classes are unequal. Therefore, a KA will never equal a non-KA A, and vice versa.