HELP

Question about the task

Resolved

I have been stuck here for many a day. I keep getting Null Point Errors or something of the sort and I understand ish why I do but I cannot see a way out of it.

Task: Each cat has a name and a mother.
Create a class that describes this situation.
Create two objects: a daughter cat and a mother.
Display them on the screen.

New task: Each cat has a name, a father, and a mother.
Edit Cat so that it reflects these relationships.
Create 6 objects: grandfather (the father's father), grandmother (the mother's mother), father, mother, son, daughter.
Display them all in the following order: grandfather, grandmother, father, mother, son, daughter.

Example input:
Grandfather Tiger Grandmother Puss Father Oscar Mother Missy Son Simba Daughter Coco

Example output:
The cat's name is Grandfather Tiger, no mother, no father The cat's name is Grandmother Puss, no mother, no father The cat's name is Father Oscar, no mother, Grandfather Tiger is the father The cat's name is Mother Missy, Grandmother Puss is the mother, no father The cat's name is Son Simba, Mother Missy is the mother, Father Oscar is the father The cat's name is Daughter Coco, Mother Missy is the mother, Father Oscar is the father

Requirements:

The program should read in the names of 6 cats in the specified order.
The main method should create 6 Cat objects.
The program should display 6 lines with information about the cats.
The line about the grandfather (first line) must match the conditions.
The line about the grandmother (second line) must match the conditions.
The line about the father (third line) must match the conditions.
The line about the mother (fourth line) must match the conditions.
The line about the son (fifth line) must match the conditions.
The line about the daughter (sixth line) must match the conditions.

package com.codegym.task.task06.task0621; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /* Cat relations */ public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); Cat noParent = new (Cat) null; //noParent = null; String grandfatherName = reader.readLine(); Cat catGrandfather = new Cat(grandfatherName, noParent, noParent); String grandmotherName = reader.readLine(); Cat catGrandmother = new Cat(grandmotherName, noParent, noParent); String fatherName = reader.readLine(); Cat catFather = new Cat(fatherName, noParent, catGrandfather); String motherName = reader.readLine(); Cat catMother = new Cat(motherName, catGrandmother, noParent); String sonName = reader.readLine(); Cat catSon = new Cat(sonName, catMother, catFather); String daughterName = reader.readLine(); Cat catDaughter = new Cat(daughterName, catMother, catFather); System.out.println(catGrandfather); System.out.println(catGrandmother); System.out.println(catFather); System.out.println(catMother); System.out.println(catSon); System.out.println(catDaughter); } public static class Cat { private String name; private Cat mother; private Cat father; Cat() { } Cat(String name, Cat mother, Cat father) { this.name = name; this.mother = mother; this.father = father; } /* Cat(String name, Cat parent, boolean sex){ this.name = name; if (sex == true) this.father = parent; this.mother = null; else this.mother = parent; this.father = null; } */ @Override public String toString() { if (mother == null) return "The cat's name is " + name + ", no mother, " + father.name + " is the father"; else if (father == null) return "The cat's name is " + name + " " + mother.name + " is the mother, no father"; else return "The cat's name is " + name + " " + mother.name + " is the mother, " + father.name + " is the father"; } } }

Comments (7)

Popular
New
Old

You must be signed in to leave a comment

Djole

Level 41 , Belgrade, Serbia

3 July 2019, 14:15

delete lines 16 and 17 and put null values for mother and father directly when creating Cat objects. You can do this because null is not an Object, it’s just a special value. In your case (lines 16,17) you declared reference noParent that points to non-existing object. Thats why you are getting NullPointerException.

Chinwe Ibegbu

Level 8 , Accra, Ghana

3 July 2019, 16:27

Thank you very much. I will try this out. But, just wondering, what happens when there's only onw parent but I have to specify mother or father?

Chinwe Ibegbu

Level 8 , Accra, Ghana

3 July 2019, 18:22

It's all good. It finally ran. I have learnt a ton of things I didn't need to because of this exercise. Thank you very much for the help. I do really appreciate it.

Djole

Level 41 , Belgrade, Serbia

3 July 2019, 18:34

you are welcome :)

Dmitriy Bursa

Level 27 , Kyiv, Ukraine

3 July 2019, 13:02

In line 37 you gettting father.name (line 75), but father = null (line 20) try first check

if ((mother == null) && (father == null)) {
    return "The cat's name is " + name + ", no mother, no father ";
}

Chinwe Ibegbu

Level 8 , Accra, Ghana

3 July 2019, 13:37

Thank you. Have implemented. Still won't run.

Chinwe Ibegbu

Level 8 , Accra, Ghana

3 July 2019, 18:22

Again, thank you for the help. It's been verified now. I'm ecstatic. Thank you, again.