Java™ How to Program, Sixth Edition - Part9

Few weeks back i started reading Java™ How to Program, Sixth Edition By H. M. Deitel - Deitel & Associates, Inc., P. J. Deitel - Deitel & Associates, Inc.

Nice book written By H. M. Deitel - Deitel & Associates, Inc., P. J. Deitel - Deitel & Associates, Inc.

I wanted to share few quotations found the book from the 9th chapter.

1) Software reuse reduces program-development time.

2) The direct superclass of a subclass (specified by the keyword extends in the first line of a class declaration) is the superclass from which the subclass inherits. An indirect superclass of a subclass is two or more levels up the class hierarchy from that subclass.

3) In single inheritance, a class is derived from one direct superclass. In multiple inheritance, a class is derived from more than one direct superclass. Java does not support multiple inheritance.

4) A subclass is more specific than its superclass and represents a smaller group of objects.

5) Every object of a subclass is also an object of that class's superclass. However, a superclass object is not an object of its class's subclasses.

6) An "is-a" relationship represents inheritance. In an "is-a" relationship, an object of a subclass also can be treated as an object of its superclass.

7) A "has-a" relationship represents composition. In a "has-a" relationship, a class object contains references to objects of other classes.

8) A subclass cannot access or inherit the private members of its superclassallowing this would violate the encapsulation of the superclass. A subclass can, however, inherit the non-private members of its superclass.

9) A superclass method can be overridden in a subclass to declare an appropriate implementation for the subclass.

10) Single-inheritance relationships form tree-like hierarchical structuresa superclass exists in a hierarchical relationship with its subclasses.

11) A superclass's public members are accessible wherever the program has a reference to an object of that superclass or one of its subclasses.

12) A superclass's private members are accessible only within the declaration of that superclass.

13) A superclass's protected members have an intermediate level of protection between public and private access. They can be accessed by members of the superclass, by members of its subclasses and by members of other classes in the same package.

14) The first task of any subclass constructor is to call its direct superclass's constructor, either explicitly or implicitly, to ensure that the instance variables inherited from the superclass are initialized properly.

15) A subclass can explicitly invoke a constructor of its superclass by using the superclass constructor call syntaxkeyword super, followed by a set of parentheses containing the superclass constructor arguments.

16) When a subclass method overrides a superclass method, the superclass method can be accessed from the subclass if the superclass method name is preceded by the keyword super and a dot (.) separator.

17) Declaring instance variables private, while providing non-private methods to manipulate and perform validation, helps enforce good software engineering.

18) Method toString takes no arguments and returns a String. The Object class's toString method is normally overridden by a subclass.

19) When an object is output using the %s format specifier, the object's toString method is called implicitly to obtain its string representation.

About the Authors

Dr. Harvey M. Deitel, Chairman and Chief Strategy Officer of Deitel & Associates, Inc., has 43 years experience in the computing field, including extensive industry and academic experience. Dr. Deitel earned B.S. and M.S. degrees from the Massachusetts Institute of Technology and a Ph.D. from Boston University. He worked on the pioneering virtual-memory operating-systems projects at IBM and MIT that developed techniques now widely implemented in systems such as UNIX, Linux and Windows XP. He has 20 years of college teaching experience, including earning tenure and serving as the Chairman of the Computer Science Department at Boston College before founding Deitel & Associates, Inc., with his son, Paul J. Deitel. He and Paul are the co-authors of several dozen books and multimedia packages and they are writing many more. With translations published in Japanese, German, Russian, Spanish, Traditional Chinese, Simplified Chinese, Korean, French, Polish, Italian, Portuguese, Greek, Urdu and Turkish, the Deitels' texts have earned international recognition. Dr. Deitel has delivered hundreds of professional seminars to major corporations, academic institutions, government organizations and the military.

Paul J. Deitel, CEO and Chief Technical Officer of Deitel & Associates, Inc., is a graduate of the MIT's Sloan School of Management, where he studied Information Technology. Through Deitel & Associates, Inc., he has delivered Java, C, C++, Internet and World Wide Web courses to industry clients, including IBM, Sun Microsystems, Dell, Lucent Technologies, Fidelity, NASA at the Kennedy Space Center, the National Severe Storm Laboratory, Compaq, White Sands Missile Range, Rogue Wave Software, Boeing, Stratus, Cambridge Technology Partners, Open Environment Corporation, One Wave, Hyperion Software, Adra Systems, Entergy, CableData Systems and many other organizations. Paul is one of the most experienced Java corporate trainers having taught about 100 professional Java training courses. He has also lectured on C++ and Java for the Boston Chapter of the Association for Computing Machinery. He and his father, Dr. Harvey M. Deitel, are the world's best-selling Computer Science textbook authors.