Cannot resolve symbol 'lang3'

This error message usually occurs when the Apache Commons Lang library is not properly imported in your project.

To fix this error, you can try the following steps:

1. Download the latest version of the Apache Commons Lang library from their official website: https://commons.apache.org/proper/commons-lang/

2. Extract the downloaded file and locate the "commons-lang3-x.x.jar" file.

3. Add the "commons-lang3-x.x.jar" file to your project's classpath. This can be done by adding it to the "lib" folder of your project or by adding it as a dependency in your build tool.

4. Finally, import the necessary classes from the Apache Commons Lang library in your code. For example, if you want to use the StringUtils class, you can add the following import statement at the beginning of your file:

import org.apache.commons.lang3.StringUtils;

By following these steps, you should be able to resolve the "Cannot resolve symbol 'lang3'" error and use the Apache Commons Lang library in your project.