CODEWITHSUNDEEP
javaarraysarraylist
Cristian Gutu
Cristian Gutu

Reputation: 1261

Why is the array.size '0'?

I have the following array: 

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

I also have a variable 'someNum':

int someNum = 12;

My code: 

public class Main {
    public static void main(String[] args){    
        int someNum = 12;
        ArrayList<Integer> myArray = new ArrayList<Integer>(someNum);
        int arraySize = myArray.size();
        System.out.println(arraySize);
    }
}

Console: '0'

Why is it printing '0'?

I checked the ArrayList documentation is states that array.size(); "Returns the number of elements in this list."

What am I doing wrong?

Upvotes: 2

Views: 165

Answers (3)

Kelsey Francis
Kelsey Francis

Reputation: 522

You're calling the ArrayList constructor that accepts as its parameter the initial capacity of the list.

You want instead

myArray = new ArrayList<Integer>();
myArray.add(someNum);

at which point myArray.size() will return 1.

Upvotes: 2

Ted Hopp
Ted Hopp

Reputation: 234795

The size is 0 because you haven't added any members. The argument to the constructor is the initial capacity, not the initial size (or the first element).

Upvotes: 9

Sotirios Delimanolis
Sotirios Delimanolis

Reputation: 279920

The constructor used in

ArrayList<Integer> myArray = new ArrayList<Integer>(someNum);

sets the initial capacity of the ArrayList. This has nothing to do with the number of elements in the ArrayList.

Upvotes: 3

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