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错误提示为：Error preverifying class example.ImageFileFilter java/lang/

NoClassDefFoundError: javax/swing/filechooser/FileFilter

大家以后不用内部类用匿名类就可以屏蔽这个问题。

Now comes an entirely new step in building your program, preverifying. Because the memory on small devices is so scarce, MIDP (actually, CLDC) specifies that bytecode verification be split into two pieces. Somewhere off the device, a preverify step is performed. The device itself is only required to do a lightweight second verification step before loading classes.

If you are using the J2ME Wireless Toolkit, you don't have to worry about preverifying class files and you may not even notice that it's happening when you click the Build button. If you'd like to understand more about preverifying, read the rest of this section. Otherwise you can just skip ahead.As you may recall, bytecode verification is one of the foundation stones of Java's runtime security model. Before a classloader dynamically loads a class, the bytecode verifier checks the class file to make sure it behaves well and won't do nasty things to the JVM. Unfortunately, the code that implements the bytecode verifier is bulky, too large to fit on a small device like a mobile phone. The CLDC dictates a two-step bytecode verification:Off the device, class files are preverified. Certain checks are performed, and the class file is massaged into a format that the lightweight second-step verifier can easily handle.On the device, the second step of verification is performed as classes are loaded. If a class file has not been preverified, it is rejected.The MIDP reference implementation and the J2ME Wireless Toolkit contain a tool called preverify that performs the first step.The preverify tools takes, as input, a class file. It produces a preverified class file. You need to specify a classpath so that the tool can find the class you want to preverify as well as any referenced classes. Finally, you can specify an output directory using the -d option. To overwrite an existing class file with a preverified version, you could do something like this:preverify -classpath .;/ midp/ classes -d . JargoneerIn this example, the -d option tells preverify to write the preverified class file to the current directory. Don't forget about inner classes, which must also be preverified. Note?/td> Splitting bytecode verification into two pieces like this has important security ramifications. Devices should only download code from trusted sources, using a secure method because some bytecode verification is performed off the device. (See Chapter 3 for more information on MIDlet suite security.) An attacker could supply malicious code that appeared to be preverified, even if it violated the rules of the full J2SE bytecode verifier. To the MIDP second-step verifier, the code would look okay and it would be loaded and run.

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