NoClassDefFoundError: org/apache/hadoop/mapred/JobConf

This error occurs when the JobConf class from the Hadoop MapReduce library is not found during runtime. The most common cause of this error is a mismatch between the version of the Hadoop MapReduce library used during development and the version used during runtime.

To resolve this issue, ensure that the correct version of the Hadoop MapReduce library is included in your classpath during runtime. It is also important to ensure that all dependencies are included in the classpath and that they are compatible with the version of the Hadoop MapReduce library being used.

If you are using Maven or another build tool, check that the dependencies are correctly specified in the project configuration file. If you are using a standalone application, ensure that all required libraries are included in the classpath when running the application.

Additionally, make sure that the Hadoop configuration files are properly set up and accessible to the application. This may include setting the HADOOP_HOME environment variable or configuring the Hadoop configuration files programmatically.

Overall, this error can be resolved by ensuring that all dependencies and configuration files are correctly set up and accessible to the application during runtime.