title: Drag and Drop in JList is not working
body: <p>So I have written a TransferHandler for my application (along the example from Oracle site) but when I am trying to move the data it is not moving. All it is doing is copying the data at index ( n-1 i.e if I am moving and item to n location) to index n. Could you please check what is wrong, though I have tried many options but none of them is working for me.</p>
  
  <pre><code>import javax.swing.TransferHandler;
  import javax.swing.*;
  import java.awt.datatransfer.*;
  
      public class ListTransferHandler extends TransferHandler {
          private int[] indices = null;
          private int addIndex = -1; //Location where items were added
          private int addCount = 0;  //Number of items added.
  
          public boolean canImport(TransferHandler.TransferSupport info) {
              // Check for String flavor
              if (!info.isDataFlavorSupported(DataFlavor.stringFlavor)) {
                  return false;
              }
              return true;
          }
  
          protected Transferable createTransferable(JComponent c) {
              return new StringSelection(exportString(c));
          }
  
          public int getSourceActions(JComponent c) {
              return TransferHandler.MOVE;
          }
  
          public boolean importData(TransferHandler.TransferSupport info) {
              if (!info.isDrop()) {
                  return false;
              }
  
              JList list = (JList)info.getComponent();
              DefaultListModel listModel = (DefaultListModel)list.getModel();
              JList.DropLocation dl = (JList.DropLocation)info.getDropLocation();
              int index = dl.getIndex();
              boolean insert = dl.isInsert();
  
              // Get the string that is being dropped.
              Transferable t = info.getTransferable();
              String data;
              try {
                  data = (String)t.getTransferData(DataFlavor.stringFlavor);
              } 
              catch (Exception e) { return false; }
  
              // Perform the actual import.  
              if (insert) {
                  listModel.add(index, data);
              } else {
                  listModel.set(index, data);
              }
              return true;
          }
  
          protected void exportDone(JComponent c, Transferable data, int action) {
              cleanup(c, action == TransferHandler.MOVE);
          }
  
          //Bundle up the selected items in the list
          //as a single string, for export.
          protected String exportString(JComponent c) {
              JList list = (JList)c;
              indices = list.getSelectedIndices();
              Object[] values = list.getSelectedValues();
  
              StringBuffer buff = new StringBuffer();
  
              for (int i = 0; i &lt; values.length; i++) {
                  Object val = values[i];
                  buff.append(val == null ? "" : val.toString());
                  if (i != values.length - 1) {
                      buff.append("\n");
                  }
              }
  
              return buff.toString();
          }
  
          //Take the incoming string and wherever there is a
          //newline, break it into a separate item in the list.
          protected void importString(JComponent c, String str) {
              JList target = (JList)c;
              DefaultListModel listModel = (DefaultListModel)target.getModel();
              int index = target.getSelectedIndex();
  
              //Prevent the user from dropping data back on itself.
              //For example, if the user is moving items #4,#5,#6 and #7 and
              //attempts to insert the items after item #5, this would
              //be problematic when removing the original items.
              //So this is not allowed.
              if (indices != null &amp;&amp; index &gt;= indices[0] - 1 &amp;&amp;
                    index &lt;= indices[indices.length - 1]) {
                  indices = null;
                  return;
              }
  
              int max = listModel.getSize();
              if (index &lt; 0) {
                  index = max;
              } else {
                  index++;
                  if (index &gt; max) {
                      index = max;
                  }
              }
              addIndex = index;
              String[] values = str.split("\n");
              addCount = values.length;
              for (int i = 0; i &lt; values.length; i++) {
                  listModel.add(index++, values[i]);
              }
          }
  
          //If the remove argument is true, the drop has been
          //successful and it's time to remove the selected items 
          //from the list. If the remove argument is false, it
          //was a Copy operation and the original list is left
          //intact.
          protected void cleanup(JComponent c, boolean remove) {
              if (remove &amp;&amp; indices != null) {
                  JList source = (JList)c;
                  DefaultListModel model  = (DefaultListModel)source.getModel();
                  //If we are moving items around in the same list, we
                  //need to adjust the indices accordingly, since those
                  //after the insertion point have moved.
                  if (addCount &gt; 0) {
                      for (int i = 0; i &lt; indices.length; i++) {
                          if (indices[i] &gt; addIndex) {
                              indices[i] += addCount;
                          }
                      }
                  }
                  for (int i = indices.length - 1; i &gt;= 0; i--) {
                      model.remove(indices[i]);
                  }
              }
              indices = null;
              addCount = 0;
              addIndex = -1;
          }
  }
  </code></pre>