Generic methods

[vuthlarhi donald]

package testapp;
import java.util.*;
/**
 *
 * @author Administrator
 */
public class ListUtils {
    public static <U> List <U> tolist(U [] array){
        List <U> list = new ArrayList<U>();
        for(U param : array){
            list.add(param);
        }
            return list;
        }
    public static <U> void addAll(List<U>list, U...array){
        for(U param : array){
            list.add(param);
    }
    }
    /**
     * 
     * @param dest 
     * @param src
     */
    public static <U> void copy(List<? super U> dest,
                            List<? extends U> src){
    
}
     public static void main(String[] args) {
//Integer[] integerArray = { 1, 2, 3, 4, 5, 6 };
//System.out.println("Array integerArray contains:");
   // tolist(list);
         
         
        
    }
 

}
 
    

how can I call the methods, to list and addAll

[Rob Spoor]

U is Integer, so:

Integer[] integerArray = { 1, 2, 3, 4, 5, 6 };
List<Integer> integerList = tolist(integerArray);
addAll(integerList, 7, 8, 9, 0); // using varargs
addAll(integerList); // using varargs but no elements
addAll(integerList, integerArray); // using direct array/
List<Integer> integerList2 = new ArrayList<Integer>();
copy(integerList2, integerList);

Although you might want to change one of the wildcards.

public static <U> void addAll(List<U>list, U...array)

You can modify this to have a List<? super U>. That way, you can use a List<Object> as well. Since the list stores U or a superclass of U, it is safe to add the array elements.