IllegalArgumentException：尝试模拟JOptionPane时的TypeMismatch

Question

为什么我在这里得到IllegalArgumentException:TypeMismatch？

@PrepareForTest({ JOptionPane.class })
...        
PowerMockito.mockStatic(JOptionPane.class)
PowerMockito.doNothing().when(JOptionPane.class, "showMessageDialog", Component.class, Object.class);

感谢您的建议！