Why doesn't it work?

Question about the task

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Help is greatly appreciated..

Create an array whose elements are lists of strings.
Fill the array with any data and display it on the screen.

Requirements:

The createList method must declare and initialize an array with ArrayList<String> elements.
The createList method must return the created array.
The createList method must add elements (string lists) to the array. The lists must not be empty.
The program should display data on the screen.
The main method must call the createList method.
The main method must call the printList method.

package com.codegym.task.task10.task1015; import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; /* Array of string lists */ public class Solution { public static void main(String[] args) { ArrayList<String>[] arrayOfStringList = createList(); printList(arrayOfStringList); } public static ArrayList<String>[] createList() { ArrayList<String> list1 = new ArrayList<String>(Arrays.asList("asd", "acf", "afrt")); ArrayList<String> list2 = new ArrayList<String>(Arrays.asList("df", "fdgz", "hzuj")); ArrayList[] array = new ArrayList[]{list1, list2}; return array; } public static void printList(ArrayList<String>[] arrayOfStringList) { for (ArrayList<String> list : arrayOfStringList) { for (String s : list) { System.out.println(s); } } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

5 August 2020, 13:28

solution

I am assuming that the task wants you to initialize an array of List<String>'s in the traditional way, such that you start with the number of elements but nothing else. Try this to replace line 22:

ArrayList<String>[] array = new ArrayList[2];
array[0] = list1;
array[1] = list2;

Prassha

Level 24 , Chagford, United Kingdom

1 August 2020, 00:13

solution

ArrayList<String>[] array = new ArrayList[2]; array[0]=list1; array[1] = list2; or use or ArrayList<String>[] array ={list1, list2}; //there is NO new keyword int [] a = new [size]; or int [] a ={1,2,3}; . my previous post is not clear. Sorry.

Seferi

Level 22 , United Federation of Planets

1 August 2020, 18:38

Thanks for replying again. It doesn't compile. Gives 'Generic array creation' error... Did you try the solutions you have given? Does it work for you?

Prassha

Level 24 , Chagford, United Kingdom

1 August 2020, 22:25

See my code: it did verified.. if this is not working just post me your exact code and i will see - or if you find out what caused the error let me know. public static ArrayList<String>[] createList() { //write your code here ArrayList<String> a1 = new ArrayList<>(); ArrayList<String> a2 = new ArrayList<>(); a1.add("wwwww"); a2.add("ddd"); ArrayList<String>[] elements=new ArrayList[2]; elements[0]=a1; elements[1]=a2; return elements; }

Seferi

Level 22 , United Federation of Planets

30 July 2020, 18:25

ArrayList<String>[] array = new ArrayList<String>[]{list1, list2};
       return array;

This doesn't work either, I really am at a lost...

Prassha

Level 24 , Chagford, United Kingdom

25 July 2020, 22:03

line 22 ArrayList<String>[] array=new ArrayList[2]; //you are initializing and declaring <String> as Gellert Varga explained. array = new ArrayList[]{list1, list2}; and remove ArrayList[] array = new ArrayList[]{list1, list2}; i hope this help.

Seferi

Level 22 , United Federation of Planets

30 July 2020, 18:06

Changed it to this, still doesn't work...

ArrayList<String> list1 = new ArrayList<>(Arrays.asList("asd", "acf", "afrt"));
    ArrayList<String> list2 = new ArrayList<String>(Arrays.asList("df", "fdgz", "hzuj"));

    return new ArrayList[]{list1, list2};
}

Gellert Varga

Level 23 , Szekesfehervar, Hungary

22 July 2020, 11:27

Requirements: "The createList method must declare and initialize an array with ArrayList<String> elements." ((This ArrayList can contain only Strings)) But in line 22 you declared an array with ArrayList elements. ((it's a general ArrayList, it can contain anything.))