PatientRecords.java

import java.util.stream.Collectors;
import java.util.Arrays;


public class PatientRecords {

    public static void main(String[] args) {

        Patient p1 = new Patient("p1", 20, "Corona", 18000);
        Patient p2 = new Patient("p2", 26, "Corona", 23000);
        Patient p3 = new Patient("p3", 29, "Cold", 6000);
        Patient p4 = new Patient("p4", 23, "Fue", 800);
        Patient p5 = new Patient("p5", 14, "Corona", 12000);

        java.util.List<Patient> patients = Arrays.asList(p1, p2, p3, p4, p5);

        patients.stream().filter(p -> p.getDisease().equals("Corona") && p.getAge() < 25).forEach(System.out::println);
        Double averageBillPaid = patients.stream().filter(p -> p.getDisease().equals("Corona")).collect(Collectors.averagingDouble(Patient::getAmount));

        System.out.println("Average bill paid: $" + averageBillPaid);
    }
}

class Patient {
    private final String name;
    private final int age;
    private final String disease;
    private final double amount;

    public Patient(String name, int age, String disease, double amount) {
        this.name = name;
        this.age = age;
        this.disease = disease;
        this.amount = amount;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public String getDisease() {
        return disease;
    }

    public double getAmount() {
        return amount;
    }

    @Override
    public String toString() {
        return "Patient{name='" + name + "', age=" + age + ", disease='" + disease + "', amount=" + amount + '}';
    }
}