"copy"(or create refrences) selected elements from one array to another

[Alexandra Fard]

Hi,

I have a problem with my java class. The red marked code gets wrong. If I type in 4 children (2 above 4 and 2 younger than 4) the system.out.println write 4 older than 4. Hope someone knows what I mean and can explain for me what I'm doing wrong. I have not the code for the Child class in this message just the main class (the problem class).

import java.util.Scanner;

public class ChildRegister {

	// Instansvariabler
	// Child lagrar "barnobjekt"
	private Child[] children;

	// Konstruktor som skapar minne för arrayen
	public ChildRegister(int size) {
		children = new Child[size];
	}

	// En metod som fyller arrayen med objekt och sätter värden
	public void initialize(Scanner keyboard, int nrOfChildren) {
		// We get the name and age from the user
		
		for (int i = 0; i < nrOfChildren; i++) {
			System.out.println("Name: ");
			String name = keyboard.nextLine();

			System.out.println("Age: ");
			int age = keyboard.nextInt();
			// rensa buffert
			keyboard.nextLine();

			children[i] = new Child(name, age);

		}
		

		for (int i = 0; i < nrOfChildren; i++){
			age = children[i].getAge();
		}
		
		

	}

	public void printAboveFour() {

		// local variabel
		int ageAboveFour = 0;

		// Create a new array children > = 4
		Child[] childrenAboveFour = new Child[children.length];
		

		System.out.println("Folowing " + "(" + childrenAboveFour.length
				+ "st) children are 4 yeras old or more:");
		for (int i = 0; i < children.length; i++) {

			// Lägger in en referens till objekten i den nya arrayen om barnen
			// är över eller lika med fyra år
			childrenAboveFour[ageAboveFour] = children[i];

			if (children[i].getAge() >= 4) {

				
				System.out.println(childrenAboveFour[ageAboveFour].toString());
			}
		}

	}

	public void printUnderFour() {

		// Locall variable
		int ageUnderFour = 0;

		// new array
		Child[] childrenUnderFour = new Child[children.length];

		// Writes nr of children younger than 4
		System.out.println( childrenUnderFour.length
				+ "st) are younger than 4");

	
		for (int i = 0; i < children.length; i++) {
			childrenUnderFour[ageUnderFour] = children[i];

			if (children[i].getAge() < 4) {

				System.out.println(childrenUnderFour[ageUnderFour].toString());

			}
		}

	}

	public static void main(String[] args) {

		Scanner keyboard = new Scanner(System.in);
		
		int nrOfChildren = 0;

		
		System.out.println("How many children do you want to register? ");
		nrOfChildren = keyboard.nextInt();
		keyboard.nextLine(); 

		ChildRegister childRegister = new ChildRegister(nrOfChildren);
		
		childRegister.initialize(keyboard, nrOfChildren);

	
		childRegister.printUnderFour();
		childRegister.printAboveFour();
	}

}

/Alexandra

[Steve Luke]

I am not understanding the problem. You create an array of length 4, then print its length and get 4. That should be the expected case. The only problem with the lines in red and how they perform is the string text. You haven't counted how many children are above or under 4 yet, so you can't print that amount out. What they text should be is 'The number of children that might possibly be under 4.'

What you need to do is StopCoding (<- link) and use a pencil and paper to figure out how you should figure out the count of children above four, and the count of children under four. Visualize what you would do if the kids were in a line and you were able to speak to them just one at a time. How would you solve problem then? Right out the steps in your native tonque (not code) then make each step shorter, more precise, and probably the number of steps more. Once you are sure you could hand your instructions to a ten year old and expect him to be able to follow them and come to the correct conclusion, then you can start coding.

[Campbell Ritchie]

Welcome to the Ranch
You should always use the code button; I have been back to your post with the code button, and you can see how much better it looks .  Note: coloured text cannot be used in code.