从jcombobox获取文件路径

Question

I am trying to select my file from the jcombobox and display the data in a text area. Currently, I have list out the file name but now once i select the filename from the dropdown its showing me this error:

SEVERE: null

This is my current code:

private void jCmboxActionPerformed(java.awt.event.ActionEvent evt) {                                       
    // TODO add your handling code here:
    //JComboBox jCmbox = (JComboBox)evt.getSource();
    String stateName = (String)jCmbox.getSelectedItem();
    updateData(stateName);

}                                      

public void updateData(String path){
    String csvFilename = "";
    URL url;
    try {
        url = new URL(csvFilename);
    } catch (MalformedURLException ex) {
        Logger.getLogger(VisualizationPanel.class.getName()).log(Level.SEVERE, null, ex);
    }
    url = VisualizationPanel.class.getResource(path);
    CSVData data = CSVData.loadFromFile(url.toString()); //loads the csv data
    VisualizationPanel visPanel = new VisualizationPanel(this, data); //draws the vis panel and adds the data to it
}

I am new to java can someone pls help me on this. Thank you.

Answer 1

In updateData() you are creating a new URL from an empty string. This is what is throwing your exception.

You can see that on the first line of updateData() you define csvFilename to be an empty string. You never reassign a value to that variable so when you come to use it in the URL constructor it is still empty.
We can see from the URL constructor spec that a the exception you are seeing will be thrown if something is wrong with the spec.
What you could do is change the line String csvFilename = ""; to String csvFilename = path; , and see if that fixes your issue.

In fact, though, since you are rewriting your URL variable straight after the try catch you should just be able to remove that block and avoid the issue completely. Try this:

public void updateData(String path){
    String csvFilename = "";
    URL url = VisualizationPanel.class.getResource(path);
    CSVData data = CSVData.loadFromFile(url.toString()); //loads the csv data
    VisualizationPanel visPanel = new VisualizationPanel(this, data); //draws the vis panel and adds the data to it
}