why it's not verified

Question about the task

Exception when working with List collections

Java Syntax, Level 9, Lesson 6

Resolved

Can somebody tell me what is wrong here

package com.codegym.task.task09.task0910; import java.util.ArrayList; /* Exception when working with List collections */ public class Solution { public static void main(String[] args) throws Exception { //write your code here try { ArrayList<String> list = new ArrayList<String>(); String s = list.get(18); } catch(RuntimeException e) { System.out.println("RuntimeException"); } //write your code here } }

Comments (6)

Popular
New
Old

You must be signed in to leave a comment

Guadalupe Gagnon

Level 37 , Tampa, United States

28 December 2018, 14:45

solution

I think this is the catch block you are looking for:

catch(IndexOutOfBoundsException e) {
   System.out.println(e.getClass());
}

IndexOutOfBoundsException is a declaration and 'e' is the variable name this means the you can name 'e' anything you want. Using that variable 'e' print the type with a call to .getClass() I figured this out by running the code first like this:

catch(Exception e) {
    System.out.println(e.getClass());
}

But the requirements specifically say "The program must catch a specific type of exception, not all possible exceptions (i.e. not Exception)". When i ran the code it printed out: class java.lang.IndexOutOfBoundsException Which i changed the "Exception" to "IndexOutOfBoundsException".

moufoulyroun kouferidji

Level 12 , New York City, United States

9 November 2019, 05:02

Frankly, Guadalupe, I m impressed with your deep technical understanding of the topics. I m really impressed. Thank you for your time and dedication!!.

Guadalupe Gagnon

Level 37 , Tampa, United States

9 November 2019, 16:32

Thanks. i'm not special or anything. You will start to get the hang of it if you stick with it too. Ive been on code gym now for over a year and had a year or so of prior experience in programming before.

The Chief

Level 18 , United States

5 April 2021, 23:04

G, is the reason this exception is an indexoutofboundsException because the arraylist's default size is 10?

The Chief

Level 18 , United States

5 April 2021, 23:05

Or is it because the arraylist is empty and it has no element with an index of 18?

Guadalupe Gagnon

Level 37 , Tampa, United States

6 April 2021, 13:45

its because it is empty. When accessing an index in an ArrayList it has to exist or the exception will occur. ArrayLists are sized dynamically, meaning that the space required to store the items is adjusted when items are added and removed, as opposed to Arrays which are sized when they are created and remains static meaning it cannot change. With Arrays you can access any index within its static size range, however with ArrayLists you can only access the items that you have put in. Example:

import java.util.*;

public class Solution {
    public static void main(String[] args) {
        // creating an ArrayList and an Array
        ArrayList<Object> test = new ArrayList<>();
        Object[] oTest = new Object[10];

        // !~ Exception would occur because index 0 does not exists ~!
        // System.out.println(test.get(0));

        print(test); // prints the ArrayList, which is blank

        // no exception because the Array has 10 indices (value would be null)
        System.out.println(oTest[5]);

        test.add(5); // added to index 0
        test.add(2); // added to index 1

        print(test); // prints the ArrayList, which has 2 values
        test.remove(1); // removes item from index 1

        // at this point the ArrayList only has 1 item
        print(test); // prints the ArrayList, which has 1 value

        // !~ Exception would occur because index 1 does not exists ~!
        // System.out.println(test.get(1));

        System.out.println(test.get(0));
    }

    static void print(ArrayList t){
        int x = t.size();
        StringBuilder sb = new StringBuilder();
        sb.append("Size of 'test' = " + x);
        if(x > 0) sb.append(" ["+0 + ":" + t.get(0));
        for(int i = 1; i < x; i++)
            sb.append(", " + i + ":" + t.get(i));
        if(x > 0) sb.append("]");
        System.out.println(sb);
    }
}