Christian Ullenboom is a Java champion and bestselling German author. His comprehensive handbook "Java is also an island" together with its counterpart about standard libraries have been introducing learners to the Java universe for the past 20 years. In his capacity as a lecturer he considers good exercise material as a vital part of the learning process. For a long time he has been creating exercises, testing them in his courses and improving his collection in the process. Constantly updated, these exercises are the basis for this book. Christian Ullenboom typed his first lines of code into the C64 at the age of 10. After many years of assembler programming and early BASIC extensions, his journey led him to the island of Java after studying computer science and psychology. For more than 20 years, Ullenboom has been an enthusiastic software architect, Java trainer, and instructor for IT specialists. His training activities have resulted in several online video courses and reference books.