Here's a simple method I use when writing a Java/Swing program that needs to place plain text (a String) on the system clipboard:

  public static void writeToClipboard(String s, ClipboardOwner owner)
  {
    Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
    Transferable transferable = new StringSelection(s);
    clipboard.setContents(transferable, owner);  }

The method takes a String as an argument, then places that string on the clipboard for you. If you have something you want to be a ClipboardOwner you can pass that in as an argument, but I often just pass a null argument to the method, like this:

    writeToClipboard(msg, null);