private boolean isAbstractClass(Class<?> targetClass) {
        return Modifier.isAbstract(targetClass.getModifiers()) && !targetClass.isInterface();
    }
Check whether a given class is deemed abstract but not an interface.

@param targetClass type to check
@return whether the indicated type represents an abstract non-interface class
jsonschema-maven-plugin/src/main/java/com/github/victools/jsonschema/plugin/maven/SchemaGeneratorMojo.java