Java：JTable更改侦听器，“对象无法转换为字符串”错误

Question

I have a JTable , and a class which is supposed to control to the program's response to various actions, the first of which I am writing is for a cell change event.

Each row is generated from a Part object, and the column class of each column is set correspondingly.

Part(String partName, String make, String partNumber,
        String altPartNumber, Double price, Integer quantity,
        String description, Boolean isAutomotive, Boolean isMarine,
        Boolean isIndustrial)
{
    //...code not shown...
}

Part objects are stored in a serializable ArrayList<Part> .

Essentially, what the event handling code needs to do is update the value of a parameter of a particular part object within this ArrayList using the updated data obtained from the JTable .

Below is the code that demonstrates how I want to do this; herein the error mentioned in the title occurs. Can anyone explain how to deal with this problem?

public class EventController extends UI implements TableModelListener
{ 
    // Declarations:

    private int row;
    private int column;

    private Part partToChange;

    // ...Omitted for brevity...
    private String updatedName;
    private String updatedMake;
    private Integer updatedQuantity;
    // Don't need declarations for the booleans, can just toggle them.

    @Override
    public void tableChanged(TableModelEvent e)
    {
        // Find out where the change took place...
        this.column = e.getColumn();
        this.row = e.getFirstRow();
        // Get the new value...

        // Send the new value to parts...
        partToChange = data.getPart(row);
        switch(column)
        {
            case 0:
                updatedName = getTableModel().getValueAt(row, column); 
                // ERROR OCCURS HERE ^
                partToChange.setName(updatedName); 
        }
    }
}

Answer 1

Your getTableModel().getValueAt(row, column); returns an Object reference and not a String, but you're assigning it to a String variable. Your choices include:

• You could cast what is returned to a String, but you risk problems if your cast is incorrect, if it in fact is not a String.
• Or you could call toString() on it. Here if it's not a String, you won't get an exception, but the String returned might not be what you want to use. A problem occurs however if the variable is null and you risk a NullPointerException if you don't check for null first. I recommend that you go this route.
• Or as per Richard Walton , by using String.valueOf() you would avoid the null exception issue of toString() . Thank you Richard!