out of Bounds Exception

but the size of a list can't be reduced automatically as i learnt in ArrayList in Pictures lesson.

Arrays are fixed and not ArrayList. When you remove an element, list size reduces.

please go through this lesson https://codegym.cc/groups/posts/21-arraylist-in-pictures-- When you remove objects from an ArrayList, the internal array's size does not decrease automatically.

list.size() returns the number of elements present in list and not the number of memory cells occupied. If there are 10 elements and you remove 5. There still be 10 memory cell occupied by list but since only 5 contains elements, it will return 5. Although another 5 elements will occupy memory space, you cannot access them as they contain nothing. It will throw outOfBoundsException. You can test it with a very simple program.

but after replacing 10000 with list.size() i'm getting the same error.

what error ? OutofBoundsException ? I just ran it. Not showing any error.

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); remove10000(arrayList); // LinkedList LinkedList linkedList = new LinkedList(); insert10000(linkedList); get10000(linkedList); set10000(linkedList); remove10000(linkedList); } public static void insert10000(List list) { //write your code here for(int i=0; i<10000; i++){ list.add(i); } } public static void get10000(List list) { //write your code here for(int i=0; i<10000; i++){ list.get(i); } } public static void set10000(List list) { //write your code here for(int i=0; i<10000; i++){ list.set(i, ""); } } public static void remove10000(List list) { //write your code here for(int i=0; i<list.size(); i++){ list.remove(i); } } }

Hello Ankush, please see the screenshot also at the bottom.

Got the problem.

for(int i=0; i<list.size(); i++){
            list.remove(i);
        }

In this, we are first removing an element and then incrementing i also. Suppose there is a list with 10 elements. You remove 0th index element. Now the element which was in 1st index will come in 0th place but you are also incrementing i which will skip the 0th place and directly move to 1st index. In this way, you are only removing 5 elements out of 10. Remove i++ from for loop and it will work.

but how it will iterate through the loop then if i remove i++ ?

It doesn't have to iterate. When you remove an element, list automatically adjusts itself and occupies the deleted element space. Consider a list [1,2,3]. If you remove one then it will become [2,3]. See, now 2 is in 0th index. Earlier it was 1. If you keep removing element at 0th index, it will remove all elements without incrementing index. You can think of it like you are stationary but list is moving itself.

yes it worked. it's better to replace for loop with while loop as it is not confusing. int i = 0; while(i < list.size()){ list.remove(i);

Yes. There are many ways. Whatever you are comfortable with. The underlying concept is the important part.

list.remove(0);

Also, You can use for loop:

for (int i = 9999; i >= 0; i--){}
for (int i = list.size()-1; i >=0; i--){}