CODEWITHSUNDEEP
javagenerics
Guillermo Alvarez
Guillermo Alvarez

Reputation: 1775

instantiating java array using generics

I am creating a list data structure and am having trouble with the generics syntax for actually using it. All I am trying to do is create an instance of ArrayLinearList<String> and of size 2 and put some strings in it. I have been trying to figure out why setting the first slot to "one" is not correct. This is the error and my code snippet.

   myList[0] = "one";

The error message is: error: incompatible types: String cannot be converted to ArrayLinearList<String>

public class ArrayLinearList<E> implements LinearListADT<E> {


 private Object[] array;
int currentSize = 0;

//Constructor (no arguments)
public ArrayLinearList() {
    currentSize = 2;  
    // array = (ArrayLinearList[]) new Object[2];   //Start with a container of size 2
    array = new Object[2];
}
   public static void main(String[] var0) {

       ArrayLinearList<String>[] myList;
       myList = new ArrayLinearList[2];
       myList[0] = "one";
   }
}

I am having quite a bit of trouble with the syntax with using generics in java. In my mind I have an array of size 2 where I am going to be placing strings. I will add more methods later but I want to understand why my current syntax is incorrect for placing this string in the array.

Upvotes: 0

Views: 110

Answers (3)

omerfarukdogan
omerfarukdogan

Reputation: 869

You need to use

myList.array[0] = "one";

Because myList is not an array. It's an object which you use to store an array within.

Upvotes: 0

SMA
SMA

Reputation: 37083

Your code here

ArrayLinearList<String>[] myList;
myList = new ArrayLinearList[2];//you have defining array myList of type ArrayLinearList
myList[0] = "one";//you are trying to store String to array which can hold ArrayLinearList

Here ArrayLinearList<String> means that your list will hold values of type String (provided we define it correctly in the code). But ArrayLinearList<String>[] will hold only reference of type ArrayLinearList and not String itself.

Upvotes: 1

szpetip
szpetip

Reputation: 333

Here:

   ArrayLinearList<String>[] myList;

you define an array that holds ArrayLinearList<String> elements, not Strings, this is why you get the error message.

Upvotes: 1

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