重启程序后为什么DataFlavor会改变？

I wrote this method

我写了这个方法

public static void printFlavors() {
    Clipboard systemClipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
    Transferable transferData = systemClipboard.getContents(null);
    for (DataFlavor dataFlavor : transferData.getTransferDataFlavors()) {
        System.out.println(dataFlavor);
    }
}
public static v