Question

Problem 3: (15 pts) Modify the Patient class with two overloaded constructors: A new default constructor which initializes the data items for a patient object using code within the constructor (use any data). A second constructor with parameters to pass all the data items into the object at the time of instantiation. Create a test main class which instantiates two objects. Instantiate the first object using the default constructor and the second object using the constructor with the parameters.

Answer 1

Default constructor with no parameters:

    public Patient(){
        this.name="John";
        this.age=69;
        this.gender='M';
        this.contact="123456";
        this.ailment="Diabetes Mellitus";
    }

Constructor with parameters:

    public Patient(String name, int age, char gender, String contact, String ailment) {
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.contact = contact;
        this.ailment = ailment;
    }

Test class with main function:

class Test{
    public static void main(String[] args) {
        Patient p1 = new Patient();
        Patient p2 = new Patient("Bob",85,'M',"987654","Arthritis");
        System.out.println("Patient 1 is: "+p1);
        System.out.println("Patient 2 is: "+p2);
    }
}

Refer the screenshot below for better understanding of the code:

7 Patient.java X Patient.java >.. 1 public class Patient{ 2 //demo data fields to store relevant information 3 private String name; 4 private int age; 5 private char gender; 6 private String contact; private String ailment; 8 9 //default constructor 10 Patient({ 11 this.name="John"; 12 this.age=69; 13 this.gender='M'; 14 this.contact="123456"; 15 this.ailment="Diabetes Mellitus"; 16 } 17 18 //paramtereized constructor 19 public Patient(String name, int age, char gender, String contact, String ailment) { 20 this.name = name; 21 this.age = age; 22 this.gender = gender; 23 this.contact = contact; 24 this.ailment = ailment; ; 25 } 26 27 //overriding tostirng() method to print the values of object. 28 @Override 29 public String toString() { 30 return "{" + 31 name='" + this.name + "" 32 , + age="" + this.age + + + 33 gender="" + this.gender + HT 34 , contact="" + this.contact + "*" + 35 ", ailment="" + this.ailment + 36 "}"; 37 } 38 } 39 40 class Test{ Run Debug 41 public static void main(String[] args) { 42 //Instantiating objects 43 Patient p1 = new Patient(); 44 Patient p2 = new Patient("Bob", 85, 'M',"987654", "Arthritis"); 45 46 //Displaying their value using the toString() fucntion. 47 System.out.println("Patient 1 is: "+p1); 48 System.out.println("Patient 2 is: "+p2); 49 } 50 } + + HER +

Output of the above code:

D: >java Test Patient 1 is: { name='John', age='69', gender='M', contact='123456', ailment='Diabetes Mellitus'} Patient 2 is: { name='Bob', age='85', gender='M', contact='987654', ailment='Arthritis'}

• In the default constructor which does not take any parameters, we define the values of fields as some sample data.
• In the parameterized constructor, we receive all the valus as parameters, and set the corresponding values of the object created, to those values using the this keyword.
• toString method is overridden to print meaningful information when printing the object.
• In main method of Test class, we instantiate two oobjects of Patient class using both constuctors and then print their values. We can see the difference in output.

For good practices, create getter and setter methods for the private data fields in Patient class like below:

public String getName() { return this.name; } public void setName(String name) { this.name = name; } public int getAge() { return this.age; } public void setAge(int age) { this.age = age; } public char getGender() { return this.gender; } public void setGender(char gender) { this.gender = gender; } public String getContact() { return this.contact; } public void setContact(String contact) { this.contact - contact; } public String getAilment() { return this.ailment; } public void setAilment(String ailment) { this.ailment = ailment; }