Part III: Scope of Variables $(7$ Points$)$

The Java language defines eight basic types that are called the primitive types. These types are not defined

by classes and, therefore, variables of these types are not objects. These types are the necessary building

blocks for all programs and represent numbers, both integers and floating $-$ point types, single characters

and the boolean values true and false.

Date Members

$1.$ Data members are declared inside the class and outside of any method.

$2.$ Data members are constants if they are modified by final, and variables, otherwise.

$3.$ If a data member is modified by static, it belongs to the class. There is only one version of a class data

member and it is shared by all objects of this type.

$4.$ If a data member is not modified by static, it is an instance data member. Each object of this type

has its own version of an instance data member.

$5.$ Data members are modified by access modifiers. So far we have used the public and private access

modifiers. Additional access modifiers are protected and to use no modifier. These modifiers determine

which outside classes have access to the data members. A complete explanation of this topic will be

given at the end of this course or the beginning of the next course.

$6.$ All data members, class or instance data, may be accessed in any instance method defined in the class.

Class methods, those that are modified by static, may only access class data members. This makes

sense, since class methods can be invoked on the class rather than on an object.

Local Variables

$1.$ Local variables are declared inside methods and include a method$$s formal parameters.

$2.$ A formal parameter of a method is known throughout the body of the method.

$3.$ A local variable declared inside the body of a method is known from the point at which it is declared

to the end of the block in which it is declared.

$4.$ Local variables are never modified by the access modifiers since they may only be accessed in the

method. They also are never modified by static.

Program

$$ A class defines a data type. The code below defines a data type called Scope $.$ This is used for illus$-$

tration purposes only, the actual purpose of this class is immaterial. Read the code for understanding

and then answer the questions that follow.

pub l ic c l a s s Scope $\{$

pr ivate s t a t i c in t one $=1$ ;

pr ivate in t two ;

pub l ic in t t h r e e ;

pub l ic s t a t i c f i n a l in t FOUR $=4$ ;

pub l ic Scope $($ in t w $,$ in t x $)$

$\{$

$//++$ i s th e auto$$in c r em en t o p e r a t o r and adds one onto th e v a l u e

one$++$;

two $=$ w ;

t h r e e $=$ x ;

$\}$

pub l ic void change $($ in t x $)$

$\{$

in t y $=$ one $+$ x ;

two $=$ one $$ y ;

$6$

t h r e e $=$ t h r e e $$ FOUR;

$\}$

pub l ic S t r i n g t o S t r i n g $()$

$\{$

return $($ one $=+$ one $+$ two $=+$ two $+$ t h r e e $=+$ t h r e e $)$ ;