Java IndexOutOfBoundsException in Arraylist

Question

Below is the code that I wrote:

 import static java.lang.System.out;
 import java.util.Scanner;
 import java.util.ArrayList;
 class Uni{
 static public void main(String...args){
 Scanner sc = new Scanner(System.in);
 ArrayList<Integer>list = new ArrayList<Integer>();
 for(int a=0,i=0;list.get(i)!=42;i++){ 
 a=sc.nextInt();
 list.add(i,a);
 }
 for(int i=0;i<list.size();i++){
 out.println(list.get(i));
 }
 }
 }

And this is the error im getting:

Execution failed. java.lang.IndexOutOfBoundsException : Index: 0, Size: 0

Stack Trace:
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(ArrayList.java:653)
at java.util.ArrayList.get(ArrayList.java:429)
at Uni.main(Uni.java:8)

Can you please help with what to do?

• mentallurg: Use debugger and it will obvious.
• Carcigenicate: What are you expecting list.get(i)!=42 to do when the list is empty?
• sns: your list is empty, also you must use try-catch while iterating such lists and list starts from 1 not 0.

Answer 1

Maybe you wanted to use a while cycle? It's much easier to initialize the list. Furthermore, your code is checking if list.get(i) is not equal to 42, but you cannot do that because your list at the index 0 is still null.

A solution could be:

import static java.lang.System.out;
import java.util.Scanner;
import java.util.ArrayList;
class Uni{
 static public void main(String...args){
 Scanner sc = new Scanner(System.in);
 ArrayList<Integer>list = new ArrayList<Integer>();
 int i = 0;
 while(i!=42) {
 list.add(i++,sc.nextInt());
 }
 for(int i=0;i<list.size();i++)
 {
 out.println(list.get(i));
 }
 }
}

EDIT: to stop after the Input is 42:

import static java.lang.System.out;
import java.util.Scanner;
import java.util.ArrayList;
class Uni{
 static public void main(String...args){
 Scanner sc = new Scanner(System.in);
 ArrayList<Integer>list = new ArrayList<Integer>();
 int i = 0
 while (true) {
 int in = sc.nextInt();
 if (in==42) break;
 list.add(i++,sc.nextInt())
 }
 for(int i=0;i<list.size();i++)
 {
 out.println(list.get(i));
 }
 }
}

• Siddharth Gupta: I wanted to stop taking input when the one of the inputs become 42 thats why I used list.get(i) != 42. Can you help me with that?