Chapter Summary

[Page 95 (continued)]

Technical Terms

access modifier

class-level variable

default value


empty string

flow of control


local variable

method call and return

null pointer

null pointer exception



reference variable

static modifier

user interface

Summary of Important Points
  • Dot notation is used to refer to an object's public elements.

  • Designing a class is a matter of deciding what role it will play and what information and actions it will have.

  • Writing a Java program is a matter of defining one or more classes. A class definition serves as a template for creating instances of the class.

  • Classes typically contain two kinds of elements, variables and methods. An object's state is defined by its instance variables.

  • Class elements declared public can be accessed by other objects. Elements declared private are hidden from other objects.

  • A class's instance variables are usually declared private and so cannot be accessed directly by other objects.

  • An object's public instance methods can be called by other objects. Thus, they make up the object's interface with other objects.

  • Object instantiation is the process of creating an object, using the new operator in conjunction with a constructor method.

  • A class definition consists of a header and a body. The header gives the class a name, and specifies its accessibility (public) and its place in the Java class hierarchy (extends Object). The class body contains declarations of the class's variables and definitions of its methods.

  • By default, a newly defined class is considered a subclass of Object.

  • Class elements declared static, such as the main() method, are associated with the class (not with its instances).

  • A Java application program must contain a main() method, which is where it begins execution.

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  • Methods used solely for the internal operations of the class should be declared private.

  • An instance variable declaration reserves memory for the instance variable within the object, associates a name and a type with the location, and specifies its accessibility.

  • A method definition consists of two parts: a header, which names the method and provides other general information about it, and a body, which contains its executable statements.

  • Declaring a variable creates a name for an object but does not create the object itself. An object is created by using the new operator and a constructor method.

Java, Java, Java(c) Object-Orienting Problem Solving
Java, Java, Java, Object-Oriented Problem Solving (3rd Edition)
ISBN: 0131474340
EAN: 2147483647
Year: 2005
Pages: 275

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