Question

My goal is to simply take my int and interpret it as an Integer trough any means, no work-arounds

I have an object Node<T> (int Key, T value).

I am working towards a program that can properly use generics, for now I just want it to use integers. However I can’t make Node<int>, I have to use Node<Integer>.

I don’t know how to read an Integer from the console, I know how to read only int.

code

public void addNumber (int number) {
   Node<Integer> newNode = new Node<Integer>(number,(Integer)number); //does not work
   this.gd.add(newNode);                                       
}

What I tried:

Integer iNumb = new Integer(number);   // Could not instantiate the type integer

and:

Node<Integer> newNode = new Node<Integer>(number, number);

I have no constructor for this, going that route would be pointless.

I’ve also tried this:

public void addNumber() throws GenericDictionary_exception {
    Scanner input = new Scanner(System.in);
    int number;
    System.out.print("Number: ");

    if (input.hasNextInt()) { 
    number = input.nextInt();
    } else
    throw new GenericDictionary_exception(
              "Error\n\t**This version only supports input of numbers**");
    
    Integer integer = number; // Type missmatch
    }

How do I take an int and cast it to Integer if generics are in play in Java?

 int num = 5;
 Integer integer = num;

That works.

Answer 1

Assuming number is an int:

Integer myInteger = number;

Java generics have some limitations, and one of them is that you can’t use primitives, you must instead use Java’s primitive wrapper classes.

Here’s a more involved explanation:

Why don't Java Generics support primitive types?

EDIT:

Just to be clear, I assume your Node class looks something like this:

public class Test {
    public static void main(String[] args) {
        int number = 2;
        Integer myInteger = number;
        Node<Integer> myNode = new Node<Integer>(number, number);
        System.out.println(myNode.getValue());
    }

    public static class Node<T> {
        private int key;
        private T value;

        public Node(int key, T value) {
            this.key = key;
            this.value = value;
        }

        public T getValue() {
            return value;
        }
    }    
}

My suggestion would be to try compiling and running this test code. If it doesn’t work, then there’s something wrong with your environment. If it does work, the problem may be something to do with your code that we’re not seeing.

EDIT 2:

This worked for me. Again, I’d suggest trying it as a standalone program:

public class Test {
    public static void main(String[] args) throws Exception {
        addNumber();
    }

    public static void addNumber() throws Exception {
        Scanner input = new Scanner(System.in);
        int number;
        System.out.print("Number: ");

        if (input.hasNextInt()) {
            number = input.nextInt();
        } else {
            throw new Exception(
                "Error\n\t**This version only supports input of numbers**");
        }

        Integer integer = number; // Type missmatch
        System.out.println(integer);
    }
}