Boxing with Arrays.asList()

[O. Ziggy]

In the following examples:

    class ZiggyTest2{
    	public static void main(String[] args){
    		
    		int[] a = { 1, 2, 3, 4,7};		
    		
    		List<Integer> li2 = new ArrayList<Integer>();
    		li2 = Arrays.asList(a); 	
    				 
    	}
    }	

The compiler complains that that int[] and java.lang.Integer are not compatible. i.e.

    found   : java.util.List<int[]>
    required: java.util.List<java.lang.Integer>
                    li2 = Arrays.asList(a);
                                   ^

It works fine if i change the List definition to remove the generic types.

    List li2 = new ArrayList();

- Shouldn't the compiler have auto-boxed the ints to Integer?
- How can i create a `List<Integer>` object from an array of ints using
Arrays.asList()?

Thanks

[John Jai]

Hi Ziggy,

It seems that boxing can be done from int -> Integer and not int[] -> Integer[]. Also the non-generic List you have shown is not a List of all the array contents, but the array itself. Try below code.

import java.util.Arrays;
import java.util.List;

public class BoxingArraysAsList {
	public static void main(String...args) {
		String[] stringArray = {"OCJP", "SCJP", "Forum"};
		List<String> stringList = Arrays.asList(stringArray);
		System.out.println("String List size -> " + stringList.size());

		int [] integerArray = {1,2,3,4};
//		List<Integer> integersList = Arrays.asList(integerArray);

		List non_genericList = Arrays.asList(integerArray);
		System.out.println("Size of non-generic list -> " + non_genericList.size());

		for (int i = 0 ; i < non_genericList.size(); i++){
			System.out.println(non_genericList.get(i));
		}
	}
}

The variable I have used is non<underscore>genericList... Not sure why underscore not shows up some time

[O. Ziggy]

Thanks John