Question

Design a Java class for Person with the following behaviours:

• talk, in which a person can talk a sentence, if s/he is at least two-year old.

• eat, in which a person can eat something if s/he is hungry. If the person eats something, then s/he becomes full (not hungry).

• needFood, in which the person’s status will become hungry if s/he is currently full.

• walk, in which a person will walk a specific distance. If a person walks more than four kilometers, then s/he becomes tired and is not able to walk anymore.

• sleep, in which a person will sleep if s/he is awake. If a person sleeps, then s/he is no tired anymore, her/him walking distance will reset, and s/he can walk again. Note that if a person is sleeping, s/he can’t walk.

• awake, in which the person is awaken if s/he is currently sleeping.

• grow, in which the person’s age will increase by one year. If a person reaches to 55, then his ability to walk will decrease by half every five years.

You need to indicate all the instance variables (properties) a give person should have to be able to handle the above list of behaviours, and store the current states of a given person. For instance, every person has name, age, current distance of walking, sleeping status, walking distance capability, etc. After designing the Person class, implement it as a Java class. Then write a tester Java program to test that class by creating some Person instance objects and do some actions for each of them. To make sure that your tester program tests all the functionalities of a given person, you have to call every method of the class at least once.

Bonus (3 points): Assume that every person can have one friend, which is another person. Therefore, two other behaviors for a person could be getFriend and changeFriend. Modify the Person class that you have designed to be able to handle these two behaviours as well. Note that you need to have another instance variable as well.

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

// Person.java

public class Person {

              // attributes

              private String name;

              private int age;

              private boolean isHungry;

              private boolean isTired;

              private boolean isSleeping;

              private double WALKING_CAPACITY = 4;

              private double distanceWalked;

              private Person friend;

              // constructor to initialize a person with given name and age

              public Person(String name, int age) {

                           this.name = name;

                           this.age = age;

                           // default values for all other fields

                           isHungry = true;// hungry

                           isTired = false; // not tired

                           isSleeping = false; // awake

                           distanceWalked = 0; // not walked any distance

                           friend = null; // no friends yet

              }

              // method to simulate talking

              public void talk() {

                           if (age >= 2) {

                                         // simulating talking

                                         System.out.println(name + " is talking");

                           } else {

                                         // could not talk

                                         System.out.println(name + " has not learnt to talk yet");

                           }

              }

              // method to simulate eating

              public void eat() {

                           if (isHungry) {

                                         System.out.println(name + " is eating food.");

                                         isHungry = false;

                           } else {

                                         System.out.println(name + " is not hungry.");

                           }

              }

              // method to simulate need for eating food

              public void needFood() {

                           if (!isHungry) {

                                         System.out.println(name + " is now hungry");

                                         isHungry = true;

                           } else {

                                         System.out.println(name + " is already hungry");

                           }

              }

              // method to simulate walking

              public void walk(double distance) {

                           if (isTired) {

                                         // tired, could not walk

                                         System.out.println(name

                                                                    + " is tired, need some sleep before walking");

                           } else if ((distance + distanceWalked) > WALKING_CAPACITY) {

                                         // distance is greater than the capacity

                                         System.out.println(name + " can't walk that far");

                           } else if (isSleeping) {

                                         // no walk while sleep

                                         System.out.println(name + " cannot walk while sleeping");

                           } else {

                                         //simulating walk

                                         System.out.println(name + " walked for " + distance + " km");

                                         distanceWalked += distance;

                                         System.out.println(name + " has now walked " + distanceWalked

                                                                    + " km without sleeping");

                                         if (distanceWalked >= WALKING_CAPACITY) {

                                                       //is now tired

                                                       isTired = true;

                                         }

                           }

              }

              // method to simulate sleeping

              public void sleep() {

                           if (isSleeping) {

                                         System.out.println(name + " is already sleeping");

                           } else {

                                         isSleeping = true;

                                         System.out.println(name + " is now sleeping");

                                         isTired = false;

                                         distanceWalked = 0;

                           }

              }

              // method to simulate waking up

              public void awake() {

                           if (isSleeping) {

                                         System.out.println(name + " is now awake");

                                         isSleeping = false;

                           } else {

                                         System.out.println(name + " is already awake");

                           }

              }

              // method to simulate growing old by 1

              public void grow() {

                           age++;

                           System.out.println(name + " is now " + age + " years old");

                           if (age >= 55) {

                                         if (age % 5 == 0) {

                                                       WALKING_CAPACITY = WALKING_CAPACITY / 2.0;

                                                       System.out.println(name + "'s walking capacity is now "

                                                                                  + WALKING_CAPACITY + " kms");

                                         }

                           }

              }

              // method to return the friend

              public Person getFriend() {

                           return friend;

              }

              // method to set a new friend

              public void changeFriend(Person newFriend) {

                           friend = newFriend;

                           if (friend != null)

                                         System.out.println(name + " is now friends with " + newFriend.name);

              }

              // returns a String containing info about all attributes

              @Override

              public String toString() {

                           String data = "Name: " + name + ", Age: " + age + "\n";

                           data += "Hungry: " + isHungry + ", Tired: " + isTired + ", Sleeping: "

                                                       + isSleeping + "\n";

                           data += "Walking capacity: " + WALKING_CAPACITY + ", Distance walked: "

                                                       + distanceWalked + "\n";

                           data += "Friend: ";

                           if (friend == null) {

                                         data += "None";

                           } else {

                                         data += friend.name;

                           }

                           return data;

              }

             

              //getter methods

             

              public String getName() {

                           return name;

              }

              public int getAge() {

                           return age;

              }

              public boolean isHungry() {

                           return isHungry;

              }

              public boolean isTired() {

                           return isTired;

              }

              public boolean isSleeping() {

                           return isSleeping;

              }

              public double getWalkingCapacity() {

                           return WALKING_CAPACITY;

              }

              public double getDistanceWalked() {

                           return distanceWalked;

              }

}

// Test.java

public class Test {

              public static void main(String[] args) {

                           //creating some Person objects

                           Person p1 = new Person("Billy", 1);

                           Person p2=new Person("Oliver", 22);

                           Person p3=new Person("John", 54);

                           //testing all methods

                           p1.talk();

                           p2.talk();

                           p3.talk();

                           p1.eat();

                           p1.eat();

                           p1.needFood();

                           p3.walk(3);

                           p3.walk(1);

                           p3.walk(2);

                           p3.sleep();

                           p3.sleep();

                           p2.awake();

                           p2.sleep();

                           p2.walk(2);

                           p1.grow();

                           p2.grow();

                           p3.grow();

                           p1.changeFriend(p2);

                          

                           System.out.println(p1);

                           System.out.println(p2);

                           System.out.println(p3);

              }

}

/*OUTPUT*/

Billy has not learnt to talk yet

Oliver is talking

John is talking

Billy is eating food.

Billy is not hungry.

Billy is now hungry

John walked for 3.0 km

John has now walked 3.0 km without sleeping

John walked for 1.0 km

John has now walked 4.0 km without sleeping

John is tired, need some sleep before walking

John is now sleeping

John is already sleeping

Oliver is already awake

Oliver is now sleeping

Oliver cannot walk while sleeping

Billy is now 2 years old

Oliver is now 23 years old

John is now 55 years old

John's walking capacity is now 2.0 kms

Billy is now friends with Oliver

Name: Billy, Age: 2

Hungry: true, Tired: false, Sleeping: false

Walking capacity: 4.0, Distance walked: 0.0

Friend: Oliver

Name: Oliver, Age: 23

Hungry: true, Tired: false, Sleeping: true

Walking capacity: 4.0, Distance walked: 0.0

Friend: None

Name: John, Age: 55

Hungry: true, Tired: false, Sleeping: true

Walking capacity: 2.0, Distance walked: 0.0

Friend: None