java.lang.UnsupportedClassVersionError：.class文件中的版本号错误？ [英] java.lang.UnsupportedClassVersionError: Bad version number in .class file?

问题描述

当我包含一个我必须从源代码编译的开源库时，我收到此错误。现在，网上的所有建议都表明代码是在一个版本中编译的，并在另一个版本中执行（旧的新版本）。但是，我的系统上只有一个版本的JRE。如果我运行命令：

I am getting this error when I include an opensource library that I had to compile from source. Now, all the suggestions on the web indicate that the code was compiled in one version and executed in another version (new on old). However, I only have one version of JRE on my system. If I run the commands:

$ javac -version
javac 1.5.0_18

$ java -version
java version "1.5.0_18"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_18-b02)
Java HotSpot(TM) Server VM (build 1.5.0_18-b02, mixed mode)

并在Eclipse中检查java库的属性，我得 1.5.0_18

and check in Eclipse for the properties of the java library, I get 1.5.0_18

因此，我必须得出一些其他内容，类本身内部正在抛出异常？这甚至可能吗？

Therefore, I have to conclude something else, internal to a class itself, is throwing the exception?? Is that even possible?

推荐答案

我已经了解到这样的错误消息通常是正确的。当它不可能（在你的脑海中）被报告的错误说出来时，你会去寻找另一个地区的问题...只是在几小时之后发现原始的错误信息确实是正确的。

I've learned that error messages like this are usually right. When it couldn't POSSIBLY (in your mind) be what the error being reported says, you go hunting for a problem in another area...only to find out hours later that the original error message was indeed right.

由于你正在使用Eclipse，我认为Thilo是正确的。你得到这个消息的最可能的原因是因为你的一个项目正在编译1.6类。如果你在系统上只有1.5 JRE并不重要，因为Eclipse有自己的编译器（不是javac），只需要1.5 JRE来编译1.6类。
这可能很奇怪，设置需要取消选中以允许这样做，但我设法做到了。

Since you're using Eclipse, I think Thilo has it right The most likely reason you are getting this message is because one of your projects is compiling 1.6 classes. It doesn't matter if you only have a 1.5 JRE on the system, because Eclipse has its own compiler (not javac), and only needs a 1.5 JRE to compile 1.6 classes. It may be weird, and a setting needs to be unchecked to allow this, but I just managed to do it.

对于有问题的项目，请检查项目属性（通常为Alt + Enter），Java编译器部分。这是一个配置为编译1.6的项目的图像，但只有1.5 JRE。

For the project in question, check the Project Properties (usually Alt+Enter), Java Compiler section. Here's an image of a project configured to compile 1.6, but with only a 1.5 JRE.

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