这也可能是因为您从具有特定包名的IDE复制了代码文件，并且希望尝试使用终端运行它。您必须首先从代码中删除包名。 这种事发生在我身上。

Java中的NoClassDefFoundError

定义:

Java虚拟机无法在运行时找到在编译时可用的特定类。 如果一个类在编译时存在，但在运行时在java类路径中不可用。

例子:

The class is not in Classpath, there is no sure shot way of knowing it but many times you can just have a look to print System.getproperty("java.classpath") and it will print the classpath from there you can at least get an idea of your actual runtime classpath. A simple example of NoClassDefFoundError is class belongs to a missing JAR file or JAR was not added into classpath or sometimes jar's name has been changed by someone like in my case one of my colleagues has changed tibco.jar into tibco_v3.jar and the program is failing with java.lang.NoClassDefFoundError and I were wondering what's wrong. Just try to run with explicitly -classpath option with the classpath you think will work and if it's working then it's a sure short sign that someone is overriding java classpath. Permission issue on JAR file can also cause NoClassDefFoundError in Java. Typo on XML Configuration can also cause NoClassDefFoundError in Java. when your compiled class which is defined in a package, doesn’t present in the same package while loading like in the case of JApplet it will throw NoClassDefFoundError in Java.

可能的解决方式:

The class is not available in Java Classpath. If you are working in J2EE environment than the visibility of Class among multiple Classloader can also cause java.lang.NoClassDefFoundError, see examples and scenario section for detailed discussion. Check for java.lang.ExceptionInInitializerError in your log file. NoClassDefFoundError due to the failure of static initialization is quite common. Because NoClassDefFoundError is a subclass of java.lang.LinkageError it can also come if one of it dependency like native library may not available. Any start-up script is overriding Classpath environment variable. You might be running your program using jar command and class was not defined in manifest file's ClassPath attribute.

资源:

3种方法解决NoClassDefFoundError

noclassdeffounderror问题模式

Java ClassNotFoundException vs NoClassDefFoundError

黑ClassLoader铝

静态与动态类加载

静态(隐式)类加载——引用、实例化或继承的结果。

MyClass myClass = new MyClass();

动态(显式)类加载是class . forname ()， loadClass()， findSystemClass()的结果

MyClass myClass = (MyClass) Class.forName("MyClass").newInstance();

每个类都有一个ClassLoader，它使用loadClass(字符串名);这就是为什么

explicit class loader uses implicit class loader

NoClassDefFoundError是显式类装入器的一部分。Error是为了保证在编译期间出现这个类，但现在(在运行时)它不存在。

ClassNotFoundException是隐式类装入器的一部分。Exception对于可以额外使用的场景(例如反射)具有弹性。

确保在module:app和module:lib中匹配:

android {
    compileSdkVersion 23
    buildToolsVersion '22.0.1'
    packagingOptions {
    }

    defaultConfig {
        minSdkVersion 17
        targetSdkVersion 23
        versionCode 11
        versionName "2.1"
    }

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");

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