同一项目的两个不同的签出副本

In my case, the problem was Eclipse's inability to differentiate between two different copies of the same project. I have one locked on trunk (SVN version control) and the other one working in one branch at a time. I tried out one change in the working copy as a JUnit test case, which included extracting a private inner class to be a public class on its own and while it was working, I open the other copy of the project to look around at some other part of the code that needed changes. At some point, the NoClassDefFoundError popped up complaining that the private inner class was not there; double-clicking in the stack trace brought me to the source file in the wrong project copy.

关闭项目的主干副本并再次运行测试用例可以解决这个问题。

我在项目中使用Spring Framework和Maven解决了这个错误。

类中存在运行时错误。我将一个属性读取为整数，但是当它从属性文件读取值时，它的值是double。

Spring没有提供运行时在哪一行上失败的完整堆栈跟踪。 它只是说NoClassDefFoundError。但是当我作为一个原生Java应用程序执行它时(将它从MVC中取出)，它给出了ExceptionInInitializerError，这是真正的原因，也是我跟踪错误的方式。

@xli的回答让我洞察到我的代码中可能存在的错误。

Java无法在运行时找到类A。 Class A在maven项目ArtClient中，来自不同的工作空间。 因此，我将ArtClient导入到Eclipse项目中。 我的两个项目使用ArtClient作为依赖项。 我将这些库引用更改为项目引用(构建路径->配置构建路径)。

问题就这样解决了。

I have had an interesting issue wiht NoClassDefFoundError in JavaEE working with Liberty server. I was using IMS resource adapters and my server.xml had already resource adapter for imsudbJXA.rar. When I added new adapter for imsudbXA.rar, I would start getting this error for instance objects for DLIException, IMSConnectionSpec or SQLInteractionSpec. I could not figure why but I resolved it by creating new server.xml for my work using only imsudbXA.rar. I am sure using multiple resource adapters in server.xml is fine, I just had no time to look into that.

此错误可能是由未检查的Java版本要求引起的。

在我的案例中，当我构建一个备受瞩目的开源项目时，通过使用SDKMAN从Java 9切换到Java 8，我能够解决这个错误。

sdk list java
sdk install java 8u152-zulu
sdk use java 8u152-zulu

然后按照下面的描述进行干净安装。

在使用Maven作为构建工具时，在禁用测试的情况下进行干净的“安装”构建有时是有帮助的，而且通常是令人满意的。

mvn clean install -DskipTests

现在已经构建并安装了所有内容，您可以继续运行测试。

mvn test

我也遇到了同样的问题，我的存货积压了好几个小时。

我找到了解决办法。在我的例子中，有一个静态方法因此而定义。JVM不能创建该类的另一个对象。

例如,

private static HttpHost proxy = new HttpHost(proxyHost, Integer.valueOf(proxyPort), "http");