How to find the similarity rate of two objects

How can you find the similarity rate of two objects expressed by a percentage? Read it below.

For example, I have two objects with the same object type. In this example we have an object ‘contact’.

Contact model class

Public class Contact {

    private String lastname;
    private String firstname;
    private String language;

    //getters & setters;
}

Now, lets say you have two contact objects:

Contact object 1

• lastname: null
• firstname: Laurent
• language: NL

Contact object 2

• lastname: Hinoul
• firstname: Laurent
• language: NL

Now we want to know what the equality is between the two classes is, expressed in a percentage. To do so, we make use of Reflect. Copy the following class in your code;

public class Equalifier {

    public int equalify(Object object1, Object object2) throws InstantiationException, IllegalAccessException {
        Map<String, Object> obj1Fields = getFieldNamesAndValues(object1);
        Map<String, Object> obj2Fields = getFieldNamesAndValues(object2);
        int same = 0;

        for (Map.Entry<String, Object> entry : obj1Fields.entrySet()) {
            Object val1 = entry.getValue();
            Object val2 = obj2Fields.get(entry.getKey());

            if (String.valueOf(val1).equals(String.valueOf(val2))) {
                same++;
            }
        }

        return (int) (((double) same / (double) obj1Fields.size()) * 100);
    }

    private Map<String, Object> getFieldNamesAndValues(final Object valueObj) throws IllegalArgumentException, IllegalAccessException {
        Class c1 = valueObj.getClass();
        Map<String, Object> fieldMap = new HashMap<String, Object>();
        Field[] valueObjFields = c1.getDeclaredFields();

        for (int i = 0; i < valueObjFields.length; i++) {
            String fieldName = valueObjFields[i].getName();
            valueObjFields[i].setAccessible(true);
            Object newObj = valueObjFields[i].get(valueObj);
            fieldMap.put(fieldName, newObj);
        }
        return fieldMap;
    }
}

Now we can test our code. Implement the following test case:

@Test
public void test() throws InstantiationException, IllegalAccessException {
    Equalifier equalifier = new Equalifier();    

    Contact contact1 = new Contact();
    Contact contact2 = new Contact();

    contact1.setLanguage("NL");
    contact1.setFirstname("Laurent");

    contact2.setLanguage("NL");
    contact2.setFirstname("Laurent");
    contact2.setLastname("Hinoul");

    assertEquals(equalifier.equalify(contact1, contact2), 66);
}

The result is that the two object are 66% equal.