Add input into list

Admin 1
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I'm trying to add user's input into list and then show it in reverse order. The elements are added until the user enters 0. Here's my code:

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class InputInArrrayList{
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int a = s.nextInt();
        List<Integer> myList = new ArrayList<>();
        while(a > 0) {
            myList.add(a);
            if (a == 0){
                break;
            }
        }
        Collections.reverse(myList);
        System.out.println(myList);
    }
}

But the loop doesn't break when it's 0. Instead, it throws OutOfMemoryError: Java Heap space. What am I doing wrong?

arraylist list collections input java
4 Answers

at least one a >= 0 needed for break to execute: 

   while(a >= 0) {
        myList.add(a);
        if (a == 0){
            break;
        }
    }
user_14874690

Please correct your loop

List<Integer> myList = new ArrayList<>();
while(true) {
    int a = s.nextInt();
    if (a == 0){
        break;
    }  else
        myList.add(a);
    }
user_76956230

Your problem is the below code:

while(a > 0) {
    myList.add(a);
    if (a == 0){
        break;
    }
}

As you can see after reading the first user input and assigning it to a, the the while loop is running infinitely. This happens because the condition argument which is the a variable never changes.
So you have to insert the part of code that updates that variable inside the while loop. Below is a simple fix:

Scanner s = new Scanner(System.in);
int a = 1;
List<Integer> myList = new ArrayList<>();
while(a > 0) {
    a = s.nextInt();
    if (a == 0) {
        break;
    } else {
        myList.add(a);
    }        
}
user_16300960

Currently , you are getting into an infinite loop as a gets set to the first number and then keeps looping, thus, keeps adding same number to the list. you need to add inside the while loop. int a = s.nextInt();

user_44840810
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