Only second condition wont verify for me when i have read from keyboard and add inputs to the list

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Hi guys, not passing second condition, not sure why when i have added strings to list using reader and loop. Rest of the conditions pass and code runs fine, please help, thanks.

1. Read 10 words from the keyboard and add them to a list of strings.
2. Determine whether the list is ordered by increasing string length.
3. If it is not, then display the index of the first element that violates this order.

Requirements:

Declare a string list variable and immediately initialize it.
Read 10 lines from the keyboard and add them to the list.
If the list is ordered by increasing string length, then you don't need to display anything.
If the list is not ordered by increasing string length, then display the index of the first element that violates this order.

package com.codegym.task.task07.task0718; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; /* Checking the order */ public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); ArrayList<String> list = new ArrayList<>(); for (int i = 0; i < 10; i++){ list.add(reader.readLine()); } ArrayList<String> helpList; helpList = list; helpList.add(0, ""); int i = 0; int k = 1; for (; i < 10; i++, k++) { if (list.get(i).length() <= helpList.get(k).length()) { } else { System.out.println(i); break; } } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

30 September 2021, 15:52

solution

The problem with the above code is that it adds 11 items to the ArrayList instead of 10. This is because lines 22 through 24 do not: - create a new list - copy the current list to that new list -then add a blank String at index 0 Instead, what they do is: -create a new variable - set that variable to point to the same exact object that 'list' points to (now they both point to the same ArrayList) - then adds a blank string to the object. To see this happening take this small bit of code, which demonstrates what the above code is doing, as an example:

// create a variable list, initialize a new object to that variable, and add 1 value to it
ArrayList<String> list = new ArrayList<>();
list.add("First Value");

//create a new list variable
ArrayList<String> helpList;
// set it to point to the object list points to
helpList = list;
// add a new value at index 0
helpList.add(0, "Value to helpList");

// print both lists:
System.out.println(list);
System.out.println(helpList);

If you run it expecting 'list' to have one value and 'helpList' to have two values, you will be surprised. Both output lines show two values because both variables ('list' and 'helpList') point to the same ArrayList object. When printing the same object the outputs are the same. To fix this you can either rewrite your code from scratch using different techniques OR just ensure that 'helpList' has a new object initialized to it on line 22/23 and copy the values in 'list' to the 'newList' object on line 24.

Bosch Testing Team

Level 12 , Karlsruhe, Germany

1 October 2021, 06:24

Thanks man, great explanation, created a whole new object and it worked