The source files for chapter5 contain the package declaration "package nia.chapter5;". Maven and the Java compiler expect to find the sources on the path "chapter5/src/main/java/nia/chapter5". Unfortunately, the path on Github is "chapter5/src/main/java/nia.chapter5". I don't know about other IDEs, but the Maven plugin for eclipse is very unhappy with that.
The source files for chapter5 contain the package declaration "package nia.chapter5;". Maven and the Java compiler expect to find the sources on the path "chapter5/src/main/java/nia/chapter5". Unfortunately, the path on Github is "chapter5/src/main/java/nia.chapter5". I don't know about other IDEs, but the Maven plugin for eclipse is very unhappy with that.