Class Cast Exception

[Lucky Singh]

Hi,
Can someone tell me why that line is giving me an exception when I run my program?

public void actionPerformed(ActionEvent e)
{
String command = (String) ((JButton)e.getSource()).getText();
if(command.equals ("submit"))
{
nameE = nameInput.getText();
locChoices = (JComboBox)(e.getSource());****CLASS CAST EXCEPTION***
locationE = (String)(locChoices.getSelectedItem());
empAgent.processFormInfo(nameE, locationE);
}
else
{
System.out.println("The reset button was pressed");
}
} //end method actionPerformed.

[Torgil Zethson]

In the first line of your actionPerformed method you successfully cast the source of the ActionEvent to a JButton. On the line where you get the ClassCastException you try to cast the same source to a JComboBox. The source of the ActionEvent can't be both a JButton and a JComboBox, so you will have to get to the JComboBox some other way. Maybe by keeping a reference to it in a member variable?

[Lucky Singh]

Thanks a lot. I was able to solve the problem. However, I cannot understand why when I add actionListener(this) to a textbox and button, it works fine but for a JComboBox and button it gives me a class cast exception.

[Torgil Zethson]

You get a ClassCastException because your implementation of actionPerformed is faulty. You can certainly use the same ActionListener for both a JButton and a JComboBox, but you must be careful when you implement it:

class Foo implements ActionListener {
 
    JButton   button;
    JComboBox combo;
 
    Foo() {
        ...
        button.addActionListener(this);
        combo.addActionListener(this);
        ...
    }
    
    public void actionPerformed(ActionEvent evt) {
        Object src = evt.getSource();
        if (src == button) {
            System.out.println("You clicked on the button.");
        }
        else if (src == combo) {
            System.out.println("You selected: " + combo.getSelectedItem());
        }
    }
}

Alternatively, if you don't want to keep member variables pointing to your button and combobox:

class Foo implements ActionListener {
 
    Foo() {
        ...
        JButton button = ...
        button.addActionListener(this);
 
        JComboBox combo = ...
        combo.addActionListener(this);
        ...
    }
    
    public void actionPerformed(ActionEvent evt) {
        Object src = evt.getSource();
        if (src instanceof JButton) {
            System.out.println("You clicked on the button " +
                ((JButton) src).getText());
        }
        else if (src instanceof JComboBox) {
            System.out.println("You selected: " + 
                ((JComboBox) src).getSelectedItem());
        }
    }
}