Delete elements from JList

Question

I have a JList that I am populating from a MySQL database. This works fine and I can see the results in a JScrollPane, however, when I execute the query again the results are added to to JList; so if there are 10 rows of data, it shows 20 after 2 queries, a copy of each row.

I want to delete all elements in the JList before re-querying so that it only shows what is there, not duplicate data.

I have:

    ArrayList<String> results;
    JList list;
    JScrollPane listScroller;
    ... //button event and arraylist population

    for(int i=0; i < list.getModel().getSize(); i++){
        list.remove(i)
    }
    list = new JList(results.toArray);
    listScroller.setViewportView(list);

When I debug it, even thought there are 50 elements, i, in the for loop, stops at 25 and then throws an exception saying 25 is out of bounds.

Any suggestions?

Answer 1

Your code is removing elements from the list (in each iteration the list's size is decremented by 1). So when you reach i==25 the list's size is 25 and when you try to remove the 25th element you are out of bounds of the list.

Try this approach:

while (list.getModel().getSize() > 0) {
    list.remove(0);
}

Edited by the OP:
The problem with list.remove(i) in your loop is that every time an element in a JList is removed the index is filled in. So if i = 0 and there are 10 elements, you remove the first and then there are only 9 elements and they take indexes 0 through 8. By the time you get to i = 5 you only have 5 elements left and 4 is the top index so you get an out of bounds exception.

Avoid this by removing the first index (0) each time.

Answer 2

You can do this without a while loop :

DefaultListModel listModel = (DefaultListModel) yourJList.getModel();
listModel.removeAllElements();

Answer 3

覆盖列表中的数据将更快。

list.setListData(new String[0])