In the development of computer programs, object-oriented programming languages have now become established in both the educational sector and industry, particularly the programming language Java. This textbook thoroughly conveys all the important concepts of object-oriented programming with Java, illustrated with many examples. The foundation of the book is a special didactic model known as the Hamster Model. This model allows programming beginners to engage playfully with the rather technical world of programming by controlling virtual hamsters through a virtual landscape and solving specific tasks along the way.