cannot find symbol listModel.addElement

Question

I am trying to create my first list, and I am stuck on an error.

Here is the template I am using for the list model:

    private ListModel getListModel() {

    String[] arrayOfStrings = new String[3];
    arrayOfStrings[0] = "one";
    arrayOfStrings[1] = "two";
    arrayOfStrings[2] = "three";

    ListModel listModel = new DefaultListModel();

    for (int i=0;i<arrayOfStrings.length;i++) {
        listModel.addElement(arrayOfStrings[i]);            
    }   
}    

The error:

error: cannot find symbol
            listModel.addElement(arrayOfStrings[i]);            

symbol:   method addElement(String)

  location: variable listModel of type ListModel

I am still new to using interfaces as well as lists. I downloaded an example code for making a list, and their code was very similar. What am I missing? I imported every single thing that the example code imported.

Answer 1

When in doubt, go to the API as it will show all. In this situation, the API will show you that the interface, ListModel<E> doesn't have an addElement(...) method. You're going to have to declare the variable as a DefaultListModel<E> type, since that is the implementation that has this method.

References:

• ListModel<E> API
• DefaultListModel<E> API

Having said this, your method could still return a ListModel interface type... e.g.,

// method declared to return the interface, ListModel
private ListModel<String> getListModel() {
    String[] arrayOfStrings = {"one", "two", "three"};

    // make sure to use generic types
    DefaultListModel<String> listModel = new DefaultListModel<>();
    for (String txt : arrayOfStrings) {
        listModel.addElement(txt);
    }
    return listModel; // don't forget to return a result
}

Answer 2

The function addElement(...) is declared in DefaultListModel, but not in ListModel, so it can only be called on an object declared as DefaultListModel.

Use DefaultListModel listModel = new DefaultListModel(); to fix your code.