How to check if a class has overridden equals and hashCode

Question

Is there a way to find out if a class has overriden equals() and hashCode() ?

Answer 1

You can use reflection

public static void main(String[] args) throws Exception {
    Method method = Bar.class.getMethod("hashCode" /*, new Class[] {...} */); // pass parameter types as needed
    System.out.println(method);
    System.out.println(overridesMethod(method, Bar.class));
}

public static boolean overridesMethod(Method method, Class clazz) {
    return clazz == method.getDeclaringClass();
}

class Bar {
    /*
     * @Override public int hashCode() { return 0; }
     */
}

will print false if the hashCode() is commented out and true if it isn't.

Method#getDeclaringClass() will return the Class object for the class where it is implemented.

Note that Class#getMethod(..) works for public methods only. But in this case, equals() and hashCode() must be public. The algorithm would need to change for other methods, depending.