Java 在Swing中复制并粘贴剪贴板异常

我尝试将字符串复制到剪贴板：

public class A {
private static final String LINE_BREAK = "\n";
private static final String CELL_BREAK = "\t";
StringSelection selection;
private Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
private StringBuffer strBuffer = new StringBuffer();
public final Action copyAll = new 
AbstractAction(ResourceBundleManager.getString(ResourceBundleManager.COPY_ALL)) {
    @Override
    public void actionPerformed(ActionEvent e) {
     strBuffer .append(LINE_BREAK);
                    selection = new StringSelection(strBuffer .toString());
                    clipboard.setContents(selection, selection);
    }};}

所以它不会复制所有字符串，我在终端中有一个例外：

ERROR: Uncaught exception in thread 'AWT-EventQueue-0': cannot open system clipboard
java.lang.IllegalStateException: cannot open system clipboard
    at java.desktop/sun.awt.windows.WClipboard.openClipboard(Native Method)

---

您是否正在AWT事件调度线程中构造

A

的每个实例？我正在构造A的一个实例（一次）以在AWT事件调度线程中使用它