how to add variable to array list and then total all the elements of arraylist?

I'm trying to input a variable into an ArrayList and then add all the elements. How can i do that? The code I开发者_开发技巧 tried is below. Thanks.

ArrayList<String> aListNumbers = new ArrayList<String>();
int abc = 23;
aListNumbers.add("abc");
aListNumbers.add("2");
aListNumbers.add("3");

//Java ArrayList Sum All Elements

int sum = 0;
for(int i=0; i < aListNumbers.size(); i++){
    sum = sum + Integer.parseInt(aListNumbers.get(i));
}

System.out.println("Sum of all elements of ArrayList is " + sum);

aListNumbers.add("abc");

Here you aren't adding the contents of the variable named abc to the list. You're adding the String "abc" to the list. This will cause a NumberFormatException when the code tries to parse the character string "abc" into a number - because "abc" just isn't a number.

aListNumbers.add(abc);

That's closer to what you want, but it will still complain because the variable abc isn't a String. Since aListNumbers expects Strings (as it is an ArrayList<String>), trying to add anything else will upset the compiler.

aListNumbers.add(Integer.toString(abc));

Will work.

Use an ArrayList<Integer> instead of String?