Store int in ArrayList and get it back to primitive variable int - Java

Use ArrayList<Integer>. When you do list.get() you will get an Integer which you can call intValue() on to get an int

(Integer)list.get(0) will do the trick. Auto-unboxing will then convert it to an int automatically

Use a type parameter rather than the raw ArrayList:

ArrayList<Integer> list = new ArrayList<Integer>();

The error you get is because you cannot cast an Object to int, autoboxing breaks down there. You could cast it to Integer and then have it autounboxed to int, but using the type parameter is a much better solution.