Question

I have a programming competition tomorrow and I have a quick question:

In Java, if you would pass an object in a parameter for a method, you actually got not a copy of the object, but the actual object.

Is it the same as C#?

public static void PunchyManager(string[] inputArray, ref int a, ref int b)
{
            string[] tempStrArray = inputArray;
}

If I do that will I basically make a pointer to inputArray, instead of having a copy?

Just a quick question, thanks!

Answer 1

In regard to your basic question in relation to Java Yes.

More generally Yes and no. Reference types (classes) are passed by reference which is like a single pointer. For something that can truly modify references outside the caller you should use the ref keyword even on reference types. This is similiar to a double pointer (assuming we are referring to pointers as they work in C for our pointer analogies).

class RefRefExample
{
    static void Method(ref string s)
    {
        s = "changed"; 
    }
    static void Main()
    {
        string str = "original";
        Method(ref str);
        // str is now "changed"
    }
}

In the above example if we passed str without using the ref keyword we would reassign the local reference of s instead of the original reference of str. By passing our reference by reference we can modify the original reference outside of the function as well. References themselves are still copied by value (but the copied reference still points to the same value) without the ref keyword.

http://msdn.microsoft.com/en-us/library/14akc2c7(v=vs.80).aspx

---

For practical usage in the scenario you are describing the modern C# idiom usually uses lists and they will likely be much faster to use as far as programming in your competition:

public static void PunchyManager(List<string> inputList, ref int a, ref int b)
{
    var tempList = new List<string>();
    foreach (var item in inputList)
       tempList.Add(item);     
}

Working on the original input list would modify objects through the reference so you would be affecting the original values outside of the method whereas the templList is a copy – Lists are very convenient.
Furthermore you can convert them back to Arrays using .ToArray()