JSF :: Finding Index Of Entry In ArrayList - Select Item

I have a JSF application with this code in the xhtml page:

<h:selectOneListbox id="selectProduct" size="10" style="width:10em; font-family:monospace" value="#{mybean.product}">
<f:selectItems value="#{mybean.products}" />
</h:selectOneListbox>

and the corresponding snippets of the Java code are:

// Class member variables
// ...
private String product;
private ArrayList<String> productValues;
private ArrayList<String> productLabels;
private SelectItem[] products;
// ... Various properties etc.
public String getLocation() { // Displayed on a page

[code]....

Most of this works correctly using only ArrayList SelectItem products without the two ArrayList and the separate SelectItem[], and the values and labels are put directly into products here. The menu works and I can select an item. However, I am unable to find the correct method for finding the index in the submit method,namely:

public void submit(ActionEvent e) {
showProduct = true;
prodNum = products.indexOf(product); // --- Here is the problem!
updateProduct();
}

which has not been changed here. In spite of trying out various ideas, prodNum always returns with -1, which means it cannot find the index of the selected product, where product is a String. Everything else seems to work correctly, and products.get(prodNum).getLabel() works if I manually give prodNum a valid index, but because it's -1 it fails.