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javaprimitive

Passing dynamic primitive type (int) to a method

In Java, the output of s is 0. I do not understand why and would it be possible to somehow get the correct value of s (1000 here)?

public static void main(String args) {
    int s = 0;
    List<Integer> list = getList(s);
    System.out.println("s = " + s);
}

public static List<Integer> getList(int s) {

    List<Integer> list = new ArrayList<Integer>();
    for (int i = 0; i < 1000; i++) {
        list.add(i); s++;
    }
}

In C# there were out descriptors to indicate that the variable is going to change if I'm not mistaken..

I'm not going to get the list.size() in general!

Solution

  • In Java, all method arguments are passed by value, i.e. copy. So, changes to the copy are not visible to the caller.

    To address your second question, you can just use list.size() on the caller side.