为什么这段代码不能编译。我正在学习用java做谓语。这是密码

package com.java8.lambda.predicate;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;

import com.java8.lambda.pojo.Employee;

public class PredicateSample {
    public static void main(String[] args) {
        Employee permanentEmployee = new Employee(70, "Jagmohan", "Sanyal", new Date(), 'M', 19900.87,"P");
        Employee tempEmployee = new Employee(70, "Shruti", "Bhatia", new Date(), 'F', 1990.87,"C");

        List<Employee> empList = new ArrayList<>();
        empList.add(permanentEmployee);
        empList.add(tempEmployee);

        PredicateSample predicateSample = new PredicateSample();
        //Code doesn't compile on this line due to non-visibility of EmployeePredicate class
        //It fails with "PredicateSample.EmployeePredicate cannot be resolved to a type"
        EmployeePredicate empPredicate = new PredicateSample().new EmployeePredicate();
    }

}

class EmployeePredicate {

    public Predicate<Employee> getOlderEmployee(){
        return p -> p.getAge() > 60  && p.getEmploymentType().equalsIgnoreCase("P");
    }

    public List<Employee> filter(List<Employee> employees, Predicate<Employee> p){
        return employees.stream().filter(p).collect(Collectors.toList());
    }
}

我已经完成了下面的链接内部类示例化
我也去了其他网站，但没能找出问题所在。