not registering the new Humans

Question about the task

Make a family

Java Syntax, Level 8, Lesson 11

Resolved

It looks right to me but it's saying that when I initialize the new human the listed children aren't legit variables

1. Create a Human class with String name, boolean sex, int age, and ArrayList<Human> children fields.
2. Create and populate objects so that we end up with: two grandfathers, two grandmothers, one father, one mother, and three children.
3. Display all the Human objects (Hint: use the Human class's toString() method).

Requirements:

The program should display text on the screen.
The Human class must have four fields.
The Human class must have one method.
The Solution class must have one method.
The program should create objects and fill them with data to get two grandfathers, two grandmothers, one father, one mother, and three children. Then it should display all the Human objects on the screen.

package com.codegym.task.task08.task0824; import java.util.*; /* Make a family */ public class Solution { public static void main(String[] args) { //write your code here ArrayList<Human> family = new ArrayList<Human>(); Human grandpa = new Human("jo", true, 88, dad); Human grandma = new Human("ja", false, 87, dad); Human grandpa2 = new Human("je", true, 88, mom); Human grandma2 = new Human("ju", false, 87, mom); Human dad = new Human("jon", true, 33, son,daughter,daughter2); Human mom = new Human("jan", false, 31, son,daughter,daughter2); Human son = new Human("joan", true, 18); Human daughter = new Human("jaon", false, 14); Human daughter2 = new Human("joon", false, 14); family.add(grandpa); family.add(grandma); family.add(grandpa2); family.add(grandma2); family.add(dad); family.add(mom); family.add(son); family.add(daughter); family.add(daughter2); System.out.println(family.toString()); } public static class Human { public String name; public boolean sex; public int age; public ArrayList<Human> children; //write your code here public Human(String name, boolean sex, int age, Human child){ this.name = name; this.sex = sex; this.age = age; this.children.add(child); } public String toString() { String text = ""; text += "Name: " + this.name; text += ", sex: " + (this.sex ? "male" : "female"); text += ", age: " + this.age; int childCount = this.children.size(); if (childCount > 0) { text += ", children: " + this.children.get(0).name; for (int i = 1; i < childCount; i++) { Human child = this.children.get(i); text += ", " + child.name; } } return text; } } }

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Rich

Level 23 , San Diego, United States

9 September 2020, 02:36

now im getting a null pointer exception for the kids toString() ....... :-\

Mayu

Level 25 , Toronto, Canada

31 August 2020, 10:27

You have made these Human instances, however there are no constructors to accept them.

Human son = new Human("joan", true, 18);
Human daughter = new Human("jaon", false, 14);
Human daughter2 = new Human("joon", false, 14);

The son, daughter, daughter2 will be seen as three different parameters. In the constructor you only have one.

Human dad = new Human("jon", true, 33, son,daughter,daughter2);
Human mom = new Human("jan", false, 31, son,daughter,daughter2);

I may suggest that you put the three children into an array list of Human, in the main method.

ArrayList<Human> childrenOfParents = new ArrayList<>();
childrenOfParents.add(children1);
childrenOfParents.add(children2);
childrenOfParents.add(children3);

And in the constructor use an array list as the parameter.

public Human(String name, boolean sex, int age, ArrayList<Human> children){
    this.name = name;
    this.sex = sex;
    this.age = age;
    this.children = children;
}

you can do the same for the children of the grandparents

hidden #10716042

Level 15

16 April 2021, 01:52

Make a family. Mayu, this was a big help in solving this one. I'd like to add that printing the children produces a null pointer error, so need to wrap the print routine with a check for a null array.

if (!(this.children == null)) { // added this check so children would print

    int childCount = this.children.size();
    if (childCount > 0) {
        text += ", children: " + this.children.get(0).name;

        for (int i = 1; i < childCount; i++) {
            Human child = this.children.get(i);
            text += ", " + child.name;
        }
    }
}

Rich

Level 23 , San Diego, United States

31 August 2020, 01:53

it still doesnt like the variable dad (or the others I'm guessing but that one is first)

MoJo

Level 17 , Cairns, Australia

Expert

30 August 2020, 19:15

I think that is because you only got one constructor, which requiers a "Human child". Since you initiate the kids without a child argument the constructer is missing an argument. Try adding a constructor that doesnt need a child argument.