How to set selected index JComboBox by value

You should use model

comboBox.getModel().setSelectedItem(object);

setSelectedItem("banana"). You could have found it yourself by just reading the javadoc.

Edit: since you changed the question, I'll change my answer.

If you want to select the item having the "banana" label, then you have two solutions:

1. Iterate through the items to find the one (or the index of the one) which has the given label, and then call setSelectedItem(theFoundItem) (or setSelectedIndex(theFoundIndex))
2. Override equals and hashCode in ComboItem so that two ComboItem instances having the same name are equal, and simply use setSelectedItem(new ComboItem(anyNumber, "banana"));