如何找到编译类的目标Java版本？

问题描述：

读取和显示Java .class版本的工具

一个编译的Java类，有没有办法从类文件告诉它的目标版本兼容性是什么？具体来说，我有一些类文件，编译为Java 6，它们运行在Java 5下，并给出无法识别的版本的错误。我想能够查看一个类文件，并找到它的目标版本兼容性是没有运行JVM。任何想法？

If I have a compiled Java class, is there a way to tell from just the class file what its target version compatibility is? Specifically, I have a number of class files, compiled to Java 6, which are running under Java 5 and giving the the "Unrecognized version" error. I want to be able to look at a class file and find what its target version compatibility is without running the JVM. Any ideas?

答

我在网上找到了这个网址，它的工作原理。

I've found this on the net and it works.

每个'.class'文件以
开头如下：

Every '.class' file starts off with the following:

魔术数字[4字节]

版本信息[4字节]

'.class'文件编译
与以下每个选项
显示：

A hexdump of a '.class' file compiled with each of the following options reveals:

javac -target 1.1 ==> CA FE BA BE 00 03 00 2D

javac -target 1.2 ==> CA FE BA BE 00 00 00 2E

javac -target 1.3 ==> CA FE BA BE 00 00 00 2F

javac -target 1.4 == > CA FE BA BE 00 00 00 30

javac -target 1.1 ==> CA FE BA BE 00 03 00 2D
javac -target 1.2 ==> CA FE BA BE 00 00 00 2E
javac -target 1.3 ==> CA FE BA BE 00 00 00 2F
javac -target 1.4 ==> CA FE BA BE 00 00 00 30

也许您可以使用这个资讯
自己的'.class'文件
版本检查实用程序，使用Java，
或者可能是脚本或shell
语言;）

Perhaps you could use this information to write your own '.class' file version checking utility, using Java, or perhaps a scripting or shell language ;) !

我希望这有助于。

Anthony Borla

From： http://bytes.com/groups/java/16603-how-determine -java-bytecode-version

如何找到编译类的目标Java版本？

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