Return an arraylist of integers

[jarco voorhees]

Hello,

I have 2 classes in my program.
From one I pass a number to the second class.
The second class does some calculations on it and stores the results in a Arraylist<integer>.
When i try to return the arraylist to the first class it gives a weird result. (Fibonacci@19821f instead of the value's )
How can I pass it correctly?

public class FibonacciTester {
	public static void main(String[] args){
		Fibonacci tester = new Fibonacci();
		tester.bereken(150);
		System.out.println(tester);
		
	}
}

import java.util.*;
public class Fibonacci {
	ArrayList<Integer> reeks = new ArrayList<Integer>();
	int i = 0;
	int waarde = 0;
	ArrayList<Integer> bereken(int getal){
		if (getal < 1){
			System.out.println("Geef een geheel getal groter dan 0 in");
		} else {
			for (waarde = 0; waarde >= getal; i++){
				reeks.add(i, waarde);
				if (waarde > 0){
					waarde = waarde + reeks.get((i-1));
				}	else {
					waarde = 1;
				}
			}//end for	
		}
		return reeks;
	}//einde bereken
}

[Mohamed Sanaulla]

This particular line:

System.out.println(tester);

prints the class name along with the hashcode value unless you have overridden the toString() method to return some meaningful String representation.

If you are using just the reference name in the println method- You should be overriding toString() to return a meaning String value for that instance.

[jarco voorhees]

mohamed sanaullah wrote:This particular line:

System.out.println(tester);

prints the class name along with the hashcode value unless you have overridden the toString() method to return some meaningful String representation.

If you are using just the reference name in the println method- You should be overriding toString() to return a meaning String value for that instance.

Hello,

I have a trouble understanding your answer.
Where exactly is the toString() used?
Is there a way to return a arraylist of integers?

[Wouter Oet]

You probably want this:

public class FibonacciTester {
	public static void main(String[] args){
		Fibonacci tester = new Fibonacci();
		ArrayList<Integer> list = tester.bereken(150);
		System.out.println(list);
		
	}
}

[jarco voorhees]

Wouter Oet wrote:You probably want this:

public class FibonacciTester {
	public static void main(String[] args){
		Fibonacci tester = new Fibonacci();
		ArrayList<Integer> list = tester.bereken(150);
		System.out.println(list);
		
	}
}

Just to be sure I understand it:

It IS possible to return an arraylist<Integer>
When you have to print it you have to Put it in another Arraylist<Integer>

This is standard practice in Java? Or is it frowned upon?


Edit: The code you provided prints: []

[Wouter Oet]

jarco voorhees wrote:Just to be sure I understand it:

It IS possible to return an arraylist<Integer>
When you have to print it you have to Put it in another Arraylist<Integer>

This is standard practice in Java? Or is it frowned upon?

It returns a reference to an ArrayList<Integer>. So yea that is possible. You don't have to assign it to a reference variable before using it.
You could also do this:

System.out.println(tester.bereken(150));

[jarco voorhees]

Wouter Oet wrote:

jarco voorhees wrote:Just to be sure I understand it:

It IS possible to return an arraylist<Integer>
When you have to print it you have to Put it in another Arraylist<Integer>

This is standard practice in Java? Or is it frowned upon?

It returns a reference to an ArrayList<Integer>. So yea that is possible. You don't have to assign it to a reference variable before using it.
You could also do this:

System.out.println(tester.bereken(150));

I am sorry but I am still struggling to understand this. Both your options return empty brackets. Why is that?

[Joanne Neal]

jarco voorhees wrote:I am sorry but I am still struggling to understand this. Both your options return empty brackets. Why is that?

Because your ArrayList is empty. Check the logic of the for loop in the bereken method.

[jarco voorhees]

Joanne Neal wrote:

jarco voorhees wrote:I am sorry but I am still struggling to understand this. Both your options return empty brackets. Why is that?

Because your ArrayList is empty. Check the logic of the for loop in the bereken method.

Oops I feel really stupid now.
I will change the loop so it works and then change the tester around until I am very sure I understand the reason behind it all.