Question

java.lang.String cannot be cast to com.wsy.JComPz.Item

图书管理系统中 图书信息修改模块 点击修改出现以下问题
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.lang.String cannot be cast to com.wsy.JComPz.Item
at com.wsy.iframe.BookModiAndDelIFrame$addBookActionListener.actionPerformed(BookModiAndDelIFrame.java:329)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
提示的329行错误 329行是如下代码：
Item item = (Item)selectedItem;
希望高手 给个解决办法 急用！！！！！！！！！！！1

Answer 1

你的转换有问题，它提示是selecteditem是String类型，不能转换成Item类型。

Answer 2

请检查selectedItem对象和你自定义Item类之间是否存在继承或实现关系。

Answer 3

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Answer 4

代码抛出异常了，你在ddBookActionListener附近看看吧 这边的代码出问题了