CodeGym/Help with Java Tasks/i don't know why error is occuring...

Level 20

Ahmedabad

25.12.2018
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11comments

i don't know why error is occuring...

Question about the task

10 thousand deletions and insertions

Java Syntax, Level 8, Lesson 6

Under discussion

Using an ArrayList and LinkedList, perform 10,000 insertions, deletions, and get and set calls.

Requirements:

The program should not display text on the screen.
The program should not read values from the keyboard.
The Solution class must contain only 5 methods.
The insert10000(List list) method must insert 10,000 items into the list.
The get10000(List list) method should call get 10,000 times on the list.
The set10000(List list) method should call set 10,000 times on the list.
The remove10000(List list) method must remove 10,000 items from the list.

package com.codegym.task.task08.task0808; import java.util.ArrayList; import java.util.LinkedList; import java.util.List; /* 10 thousand deletions and insertions */ public class Solution { public static void main(String[] args) throws Exception { // ArrayList ArrayList arrayList = new ArrayList(); insert10000(arrayList); get10000(arrayList); set10000(arrayList); arrayList.add(33); arrayList.add(22); remove10000(arrayList); // LinkedList LinkedList linkedList = new LinkedList(); insert10000(linkedList); get10000(linkedList); set10000(linkedList); linkedList.add(34); linkedList.add(3); remove10000(linkedList); } public static void insert10000(List list) { for (int i = 0 ;i < 10000 ; i++) { list.add(i); } } public static void get10000(List list) { for(int i = 0 ; i < 10000 ; i++) { list.get(i); } } public static void set10000(List list) { for(int i = 0 ; i < 10000 ; i++) { list.set(i , " "); } } public static void remove10000(List list) { for(int i = 1 ; i <= 10000; i++) { list.remove(i); } } }

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Alban

Level 14 , Kukes, Albania

8 October 2020, 07:53

First "import java.util.Random;" at line 6. And than use this code; public static void remove10000(List list) { //write your code here Random rand = new Random(); for (int i=0; i<10000; i++) { int n = rand.nextInt(list.size()); list.remove(n); } Hope to help you

ashley819

Level 9 , Washington DC, United States

26 June 2020, 01:29

Instead of a for loop in the remove10000 method, you can use a while loop:

int i = 0;
while (!list.isEmpty()) {
    list.remove(i);
 }

This way you always remove index 0.

Naveen Muralidoss

Level 9 , Newark, United States

3 October 2019, 20:51

use Iterator to remove the elements , i hope below should work Iterator iterator = list.iterator(); while(iterator.hasNext()){ iterator.next(); iterator.remove(); }

Thang Za Thang

Level 18 , Melbourne, Australia

24 June 2020, 01:52

Also remember to import import java.util.*; so the iterator works

雪锋李

Level 8 , Guangzhou, China

16 July 2019, 13:55

for(int i=0;i<10000;i++) list.remove(0); because every time,you remove the list,the size is change.so dont use list.size() as the flag;we should remove the first one in every turns.

Suma

Level 11 , Hyderabad, India

18 June 2019, 08:01

for(int i=list.size()-1; i>= 0 ; i--) { list.remove(i); } This should work. We are trying to delete by incrementing i here and hence it is failing because the list keeps decreasing.

Profj

Level 20 , Lagos, Nigeria

8 June 2019, 21:39

Use remove(0). It will work

Shreyas Joshi

Level 16 , Mumbai, India

27 February 2019, 17:54

public static void remove10000(List list) { //write your code here for(int i = 0; i < 10000; i++) { list.remove(0); }

Guadalupe Gagnon

Level 37 , Tampa, United States

26 December 2018, 00:31

#1 line 59: for(int i = 1 ; i <= 10000; i++) your one problem is here. make that like all the other ones: for(int i = 0 ; i < 10000 ; i++) The verify system will test your code by running it with a list of 10000 numbers, which has a max index of 9999. It will error out and fail every time at the last sequence of the loop. #2 what Khurram said. He said you are removing by index i which shifts the remaining index numbers down one. Solve this by always removing index 0.

Khurram

Level 16 , Lahore, Pakistan

25 December 2018, 15:15

in the remove function you are removing 1 element in every loop, so the index of the remaining elements moves up by 1, (index 1 becomes 0, 2 becomes 1 and so on), so when i reaches 5001, there is no index 5001 in the list because the elements are being removed and the remaining indices move up by 1, that is why you are getting an index out of bounds error also, you have added 2 extra elements in the lists which is not required

Michael Martin

Level 19 , Arlington, United States

25 December 2018, 15:10

Why do you have lines that add things to the lists? Like this:

arrayList.add(33);
arrayList.add(22);

After the remove10000() method is called, your lists should be empty, but you have 2 extra items in them.