Refactoring code to be Generics and functional interface

I have two interfaces one can be used to find some statistics by Key and Value and the other is used to visit an object and iterate over it, the first one has the following methods:

public interface Statistic {

    public String getKey();

    public Object getValue();

    public String getDetails();
}

And here is the implementation for it:

public class Collector implements Statistic {

    private String key;
    private int val;

    public Collector(String key, int val) {
        this.key = key;
        this.val = val;
    }

    public void setValue(int val) {
        this.val = val;
    }

    @Override
    public String getKey() {
        return key;
    }

    @Override
    public Integer getValue() {
        return val;
    }

    @Override
    public String getDetails() {
        return null;
    }
}

And the other one has the following:

public interface StatisticsCollector<T extends Object, S extends Statistic> {

    public String getName();

    public void visit(T object);

    public Iterator<S> calculatedStatistics();
}

And here is the implementation for it:

public class CalculateFromObject<K, V> implements StatisticsCollector<Object, Collector> {

    EmployeeValidator empValidator = new EmployeeValidator();
    StringValidator strValidator = new StringValidator();

    @Override
    public String getName() {
        return null;
    }

    @Override
    public void visit(Object object) {
        if (object instanceof String) {
            String str = object.toString();

            int upperCaseCount = strValidator.upperCaseFreq(str);
            strValidator.set.add(new Collector("Upper Case Letters: ", upperCaseCount));
            int lowerCaseCount = strValidator.lowerCaseFreq(str);
            strValidator.set.add(new Collector("Lower Case Letters: ", lowerCaseCount));
            int digitsCount = strValidator.digitFreq(str);
            strValidator.set.add(new Collector("Digits Count: ", digitsCount));
            int wordCount = strValidator.wordFreq(str);
            strValidator.set.add(new Collector("Words Count: ", wordCount));
            int nonWordCount = strValidator.nonWordFreq(str);
            strValidator.set.add(new Collector("Non Word Count: ", nonWordCount));

        } else if (object instanceof Employee) {

            Employee emp = (Employee) object;
            empValidator.salaryValidator(emp);
            empValidator.birthDateValidator(emp);
            empValidator.birthPlaceValidator(emp);
            empValidator.resignationDateValidator(emp);
            empValidator.positionValidator(emp);
        }
    }

    @Override
    public Iterator<Collector> calculatedStatistics() {
        return empValidator.set.iterator();
    }


}

And in my package I have a bean for Employee which has few properties like firstName, lastName, salary and position with their setters and getters.

I would like to do some validations like get me the number of employees which has a salary of x and been born in 1990 and did the following class for these validations:

public class EmployeeValidator {

    public Set<Collector> set = new HashSet<>();

    public void salaryValidator(Employee emp) {
        int count = 0;
        // each collector consist of a condition (function), key, value (always incremented)
        if (emp.getSalary() < 350) {
            set.add(new Collector("Employee with salaries less than 350JD: ", ++count));
        } else if (emp.getSalary() >= 350 && emp.getSalary() < 600) {
            set.add(new Collector("Employee with salaries between 350JD And 600JD: ", ++count));
        } else if (emp.getSalary() >= 600 && emp.getSalary() < 1200) {
            set.add(new Collector("Employee with salaries between 600JD And 1200JD ", ++count));
        } else if (emp.getSalary() >= 1200) {
            set.add(new Collector("Employee with salaries more than 1200JD: ", ++count));
        }

    }

    public void birthDateValidator(Employee emp) {
        for (Collector stats : set) {
            if (("Employees that where born in " + emp.getBirthDate().getYear() + " = ").equals(stats.getKey())) {
                count(stats);
                return;
            }
        }
        set.add(new Collector("Employees that where born in " + emp.getBirthDate().getYear() + " = ", 1));
    }

    public void birthPlaceValidator(Employee emp) {
        for (Collector stats : set) {
            if (("Employees that where born in " + emp.getBirthPlace() + " = ").equals(stats.getKey())) {
                count(stats);
                return;
            }
        }
        set.add(new Collector("Employees that where born in " + emp.getBirthPlace() + " = ", 1));
    }

    public void resignationDateValidator(Employee emp) {
        for (Collector stats : set) {
            if (("Employees that where Resignation in " + emp.getResignationDate().getYear() + " = ").equals(
                    stats.getKey())) {
                count(stats);
                return;
            }
        }
        set.add(new Collector("Employees that where Resignation in " + emp.getResignationDate().getYear() + " = ", 1));
    }

    public void positionValidator(Employee emp) {
        for (Collector stats : set) {
            if (("Employees that occupy the " + emp.getPosition() + " position = ").equals(stats.getKey())) {
                count(stats);
                return;
            }
        }
        set.add(new Collector("Employees that occupy the " + emp.getPosition() + " position = ", 1));
    }

    private void count(Collector stats) {
        int counter = stats.getValue() + 1;
        stats.setValue(counter);
    }
}

And I have another class to validate strings and see how many uppercase letters a string has, how many lower case it has...etc

As you can see in the visit method in the CalculateFromObject class im calling all my methods to do the validations, everything is working fine and I am getting the expected results, but my code is not very efficient as I would like to make it generic and make it accept any type of object, I have done few tries but im stuck.

I have tried to write a functional interface called Conditions that has one method that I can pass a condition and check it like the following:

public interface Conditions {

    boolean checkCondition(Object obj);

}

So can someone suggest what is the best way to change my code to be generic and accept any type of objects like Student for example and to be as clean as possible maybe by applying a design pattern?