Java.lang.ClassFormatError: EDU/oswego/cs/dl/util/concurrent/ConcurrentRead

Question

Hi,
I try to load an XML-File into my Applet with jdom4. But when reading in the Document with the SAX-Reader I get this Error:
java.lang.ClassFormatError: EDU/oswego/cs/dl/util/concurrent/ConcurrentReaderHashMap (Bad magic number)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at sun.applet.AppletClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at org.dom4j.tree.NamespaceCache.<clinit>(NamespaceCache.java:48)
at org.dom4j.Namespace.<clinit>(Namespace.java:24)
at org.dom4j.DocumentFactory.createNamespace(DocumentFactory.java:161)
at org.dom4j.tree.NamespaceStack.createNamespace(NamespaceStack.java:286)
at org.dom4j.tree.NamespaceStack.getQName(NamespaceStack.java:167)
at org.dom4j.io.SAXContentHandler.startElement(SAXContentHandler.java:221)
at org.apache.crimson.parser.Parser2.maybeElement(Unknown Source)
at org.apache.crimson.parser.Parser2.parseInternal(Unknown Source)
at org.apache.crimson.parser.Parser2.parse(Unknown Source)
at org.apache.crimson.parser.XMLReaderImpl.parse(Unknown Source)
at org.dom4j.io.SAXReader.read(SAXReader.java:334)
at org.dom4j.io.SAXReader.read(SAXReader.java:236)
at client.Load.<init>(Load.java:42)
at client.Login.startLoad(Login.java:183)
at client.ParamTimer.run(ParamTimer.java:30)
I use JRE 1.4.2_05! With JRE 1.5 I get a warning and then the JRE switches to his own SAX Parser.
How can I solve this???
Greets

Answer 1

The error message says that the class file has a bad "magic number." Magic number is the first four bytes of a .class file and in a valid file they should be CA FE BA BE (in hex); "bad magic number" means that the first four bytes are something else and therefore it's not a valid Java .class file.