Java - jList getSelectedValue problem

Question

I am trying to convert an object (selected item on jList1) to a string but it is returning null.

I have tried:

Object object1 = jList1.getSelectedValue();
String string1 = object.toString();

&

String string1 = jList1.getSelectedValue().toString();

But they are both returning null for me, is there something I am doing wrong?

This is what happens when button1 is pressed:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    Object object1 = jList1.getSelectedValue();
    String string1 = object1.toString();
    System.out.println(string1) 
}

@Evan, that gives a Type Mismatch error (Cannot convert an object to string) — Jamie
– Jamie, Commented Sep 5, 2011 at 16:02
Okay, just making sure. The documentation examples for JList are unclear about how the return value is handled. — Evan Mulawski
– Evan Mulawski, Commented Sep 5, 2011 at 16:04

Péter Török · Accepted Answer · 2011-09-05 15:56:25Z

5

What type is this object? Have a look at the class's toString method if you can - chances are it is returning (incorrectly) null.

If getSelectedValue() returns a valid object, this is the only way for you to get null. If however it returned null, you should get a NullPointerException upon trying to call toString on the null reference. So I see no other possibility (provided the code snippet you posted is exact and your description is correct).

answered Sep 5, 2011 at 15:56

Péter Török

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2 Comments

Jamie Over a year ago

I believe it is the getSelectedValue() that is returning null and the snippets I posted above are what I am trying to use aswell as the description.

Péter Török Over a year ago

@Jamie, why don't you add a debug printout to test your theory? E.g. if (object1 == null) System.out.println("selected value is null");

James DW · Accepted Answer · 2011-09-05 15:55:49Z

1

Chances are the toString() method on the selectedValue is returning null.

Has it been implemented properly?

answered Sep 5, 2011 at 15:55

James DW

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3 Comments

Jamie Over a year ago

I believe it is, although I do have something selected on the jList.

Rakesh Over a year ago

int index = jList1.getSelectedIndex(); use this to see if actually any of the value from the list is selected or not. If it is returning -1, then no value is selected.

Jamie Over a year ago

@Rakesh, That returns 0, 1, 2, etc depending on which item was selected.

Jamie · Accepted Answer · 2011-10-02 12:39:41Z

-4

Sorted this myself, not sure what was wrong but I copied the GUI and most of the code (apart from that section causing problems) to a new project re-wrote that part and it worked.

edited Oct 2, 2011 at 12:39

answered Sep 6, 2011 at 16:17

Jamie

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1 Comment

James DW Over a year ago

This answer doesn't help others who might come across the same problem.

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