如何对arraylist的所有元素求和

Question

So I'm making a GUI where basically the user inputs a series of numbers into an array list and I'm trying to make it so i can get the sum of all the numbers the add in. Here is what I have :

sum = 0;
for(int i=0; i<numberlist.size(); i++){
    sum += numberlist.get(i);
}
Output.setText("The Sum of all the numbers is " + sum);
}

I get an error message that says:

inconvertable types. 
required : int 
found: java.lang.string

Answer 1

I'm betting you have an ArrayList<String> . This means that your numbers are stored as a String . So what you should do is use an ArrayList<Integer> and then parse the strings you get with Integer.parseInt(yourinputstring) and then add that to the ArrayList.

Answer 2

You can use Integer.parseInt(String) like so

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

Answer 3

It seems that your GUI takes user inputs as String list.

In this case Try:

sum+=Integer.parseInt(numberlist.get(i));

Answer 4

Just from looking at this snippet, I would assume that you have to convert "numberlist.get(i)" to an int.

sum = 0;
for(int i=0; i<numberlist.size(); i++){
    sum += Integer.parseInt(numberlist.get(i));
}
Output.setText("The Sum of all the numbers is " + sum);
}

Answer 5

according to error:

inconvertable types. required : int found: java.lang.string

you defined an ArrayList of String which contains inputed numbers, so to sum these numbers firstly you need to convert the String of number to a number and then sum them:

1. if the values are Integer then try to use Integer.parseInt() or Integer.valueOf()
2. if the values are Double then try to use 'Double.parseDouble()' or 'Double.valueOf()'
3. Long.parseLong() or Long.valueOf()
4. more details about number

ArrayList<String> numberlist = new ArrayList<>();
numberlist.add("1");
numberlist.add("2");
numberlist.add("3");
int sum = 0;
for (int i = 0; i < numberlist.size(); i++) {
    sum += Integer.valueOf(numberlist.get(i));
}
Output.setText("The Sum of all the numbers is " + sum);