The second chapter in the book introduces array in greater detail. This makes a great deal of sense since many of the algorithms the book is going to cover are built on arrays.
The priority queue algorithm also introduced in Chapter four is the first that that uses methods that actually include more than a single line of code.
Each of the chapters dealing with a particular algorithm follows the same format. First it describes what the algorithm is. Next it describes the methods needed to implement the algorithm and finally it provides the code for those methods and show you how to use them.
The later chapters are more useful because they show more complex algorithms and how to implement them.