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Tip of the Day
Language: Java Language
Expertise: Beginner
Apr 9, 1997



Application Security Testing: An Integral Part of DevOps


What does it mean when I receive the Java:java.lang.ClassFormatError? I get it whenever I try to implement a ready-made Java application onto my Web site.

The ClassFormatError is thrown whenever the class loader determines the file is malformed or cannot be interpreted as a class file.

I noticed you used the word "application" when describing your Java program. Of course to run under a browser, a Java program must extend the class Applet and provide an init() method.

Other common reasons for this error are:

  • Forgot to compile the .java file into a .class file
  • ftp'd the .class file as a text file
  • Specified the .java file instead of the .class file in the HTML APPLET tag.
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