I have this assignment where I'm only allowed to change the signature of the methods. I have a class utility and a test class. Th issue I'm having is that i keep getting argument errors. Here is the Utility Class

public class Utility <T extends Comparable<T>> {  //Change this line to create a parameterized class
    
    // Insert your code here
    public ArrayList<T> list;
    
    public Utility() {
        list = new ArrayList<T>();
    }
    
    public Utility (List<T> list) { 
        this.list = (ArrayList<T>) new ArrayList<>(list);
    }

    public void mergeList(List<T> list) { //This is the method that the error refers to
        for (T obj: this.list)
            list.add(obj);
    }
}

This is the test that keeps giving me errors

void testMergeList2() {
        List<Integer> myList = new ArrayList<Integer>(); 
        myList.add(0); 
        myList.add(1); 
        myList.add(2); 
        myList.add(3); 
        Utility<Integer> ut = new Utility<Integer>(myList); 

        List<Number> myList2 = new ArrayList<Number>(); 
        myList2.add(0); 
        myList2.add(1); 
        myList2.add(2); 
        myList2.add(5); 
        ut.mergeList(myList2);      //This is where I get the error 
        boolean actual = true;
        for (int i= 0; i < 4; i  ) {
            if ((Integer) myList2.get(i) != i || (Integer)myList2.get(i 4)!= i) {
                actual = false; 
                break; 
            }
        }

        boolean expected = false; 
        assertEquals(expected, actual, "mergeList Failed! "   expected   " expected but "  actual   " is given");
        
        
    }

I tried changing T for something else but then the compiler tells me to cast T which I'm not allowed to do since I can't change the body of the method.

CodePudding user response：

Your Utility is declared using Integer however the myList2 is using Number. Those are incompatible types.

In order to fix this, change mergeList(List<T> list) to just mergeList(List list). This will work and your test will pass.