java.lang.ClassCastException : java. lang.Float 无法转换为 java.lang.String

Question

java.lang.ClassCastException: java.lang.Float cannot be cast to java.lang.String

我在以下代码中遇到此异常:

String colValue= (String)data_ForSave.elementAt(r).get(ColValindex);

其中 ForSave 是包含表值的 String vector ，我不明白为什么会抛出此异常。

下面是异常的完整堆栈跟踪。

异常堆栈跟踪

java.lang.ClassCastException: java.lang.Float cannot be cast to java.lang.String
at Utilities.Utility.DataHeaderMapping(Utility.java:1122)
at jewelleryerpapplication.GUI.ProductsInformation.jbtnSaveActionPerformed(ProductsInformation.java:4222)
at jewelleryerpapplication.GUI.ProductsInformation.access$1500(ProductsInformation.java:40)
at jewelleryerpapplication.GUI.ProductsInformation$37.actionPerformed(ProductsInformation.java:3292)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2713)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
at java.awt.EventQueue.access$000(EventQueue.java:101)
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:680)
at java.awt.EventQueue$4.run(EventQueue.java:678)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Row   : 0

非常感谢您提供答案，因为我一直坚持这一点。

Answer 1

从您的评论看来，您使用的泛型类型不正确。

例如

Vector g = new Vector();
List list = new ArrayList();
list.add(1.0f);
g.add(list);

Vector<List<String>> grid = g; // incorrect cast, but only a warning.
String s = g.elementAt(0).get(0); // throws a class cast exception.

顺便说一句:我不知道为什么要结合使用 elementAt(index) 和 get(index)，因为除非 Swing 需要，否则它们是旧样式(Java 1.2 之前)和更新样式(Java 1.2 之后)。 ;)

---

我会用它来反转不正确的泛型，尽管修复类型会更好。

List list = (List) data_ForSave.elementAt(r);
String colValue= String.valueOf(list.get(ColValindex));

因为您不能将 Float 转换为 String。您可以改为将其转换为字符串。