I'm trying to add apache-commons to my fresh project but I got problems with packages after importing the source.
The declared package "org.apache.commons.math" does not match
the expected package "src.main.java.org.apache.commons.math"
Packages in Java translate into a folder hierarchy, both for the source files and the compiled class files. A Source Folder expected to contain the package
org.apache.commons.math will contain files in a structure like
org/apache/commons/math/ where the Source Folder is the direct parent of
org. Having an expected package of
src.main.java.org.apache.commons.math means that
src/main/java is in a Source Folder rather that being set as a Source Folder. Open your project's Properties dialog, go to the Java Build Path page, and correct the contents of the Source tab. If you're using Maven or another tool to compile your sources instead, fix that configuration directly.