| << Chapter < Page | Chapter >> Page > |
| Listing 19 - More cShow method code. |
|---|
System.out.println("-6-");//separator
System.out.println(A.this.getClass().getName()); |
| Listing 20 - More cShow method code. |
|---|
System.out.println("-7-");
System.out.println("In cShow, bVar = " + refToB.bVar);
System.out.println(refToB.getClass().getName());
System.out.println("In cShow, aVar = " + refToA.aVar);
System.out.println(refToA.getClass().getName()); |
| Listing 21 - More cShow method code. |
|---|
System.out.println("-8-");
refToB.bShow(); |
| Listing 22 - More cShow method code. |
|---|
System.out.println("-9-");
refToA.aShow(); |
| Listing 23 - Overridden toString method in class C. |
|---|
public String toString(){
return "toString in Class C";}//end overridden toString |
| Listing 24 - More cShow method code. |
|---|
System.out.println("-10-");
System.out.println("className = " + className);
System.out.println(toString());System.out.println(
"className = " + super.className);System.out.println(super.toString());
}//end cShow method |
Listing 25 - Complete program listing.
/*File InnerClasses06.java
Copyright 2003 R.G.BaldwinRev 6/22/03
Illustrates the use of member classes. Class Bis a member class of class A. Class C is a
member class of class B. Class D is a privatemember class of class C. An object is
instantiated from the class named A, which makesit possible to instantiate an object of the
member class named B. According to Flanagan,this causes the object of the Class B to be
internally associated with the object of theclass named A. The object of the class named B
is used to instantiate an object of the memberclass named C. This object is internally
associated with the object of the class B.When the object of the class C is instantiated,
the constructor for that class instantiatesseparate objects of the classes named A and B and
also instantiates an object of the private memberclass named D. The new and separate object of
the class B continues to be internally associatedwith the original object of the Class A.
A variety of operations are performed from withinmethods belonging to the object of the Class C to
illustrate the various characteristics of objectsinstantiated from member classes. Comments in
the code explain the purpose of each of thoseoperations.
The compilation of this program produces thefollowing class files:
A$B$C$D.classA$B$C.class
A$B.classA.class
InnerClasses06.classX.class
The output from this program is shown below:In xstr for A, objCntA = 1
In xstr for B, objCntB = 1In xstr for C, objCntC = 1
Construct obj of private class D.Private class file name: A$B$C$D
In xstr for A, objCntA = 2In xstr for B, objCntB = 2
-1-In cShow, objNumber = 1
In cShow, cVar = 3-2-
In bShow, bVar = 2In bShow, objNumber = 1
In aShow, aVar = 1In aShow, objNumber = 1
-3-In aShow, aVar = 1
In aShow, objNumber = 1-4-
A$B$CA$B$C
A$B$CA$B$C
A$B$C-5-
A$BA$B
-6-A
-7-In cShow, bVar = 20
A$BIn cShow, aVar = 10
A-8-
In bShow, bVar = 20In bShow, objNumber = 2
In aShow, aVar = 1In aShow, objNumber = 1
-9-In aShow, aVar = 10
In aShow, objNumber = 2-10-
className = CtoString in Class C
className = XtoString in Class X
Tested using SDK 1.4.1 under WinXP************************************************/
public class InnerClasses06{public static void main(String[] args){//Instantiate an object of the member class
// named C. Note that it is necessary to// instantiate objects of the enclosing
// classes as well. Then invoke the public// method named cShow on the object of the
// class named C.new A(1).new B(2).new C(3).cShow();
}//end main}//end class InnerClasses06
//=============================================////This class will be extended by the class named
// C, which is a member of the class named B,// which is a member of the class named A. This
// will illustrate that the inheritance// hierarchy is independent of the containment
// hierarchy.class X{//extends Object by default
protected String className = "X";//Override the toString method
public String toString(){return "toString in Class X";
}//end overridden toString}//end class X
//=============================================//class A{
private int aVar;private static int objCntA = 0;
//Cannot place static variable in inner class.// Place it here instead.
private static int objCntB = 0;//Cannot place static variable in inner class.
// Place it here instead.private static int objCntC = 0;
private int objNumber = 0;A(int val){//top-level class constructor
aVar = val;objCntA++;//Increment object counter
//Record the number of the object being// instantiated
objNumber = objCntA;System.out.println(
"In xstr for A, objCntA = " + objCntA);}//end constructor
//-------------------------------------------//private void aShow(){
System.out.println("In aShow, aVar = " + aVar);
System.out.println("In aShow, objNumber = " + objNumber);
}//end aShow//===========================================//
//Note that this class is defined internal to// the class named A.
class B{//member class of Aprivate int bVar;
private int objNumber = 0;B(int val){//constructor
bVar = val;//Increment static variable in top-level
// classA.objCntB++;
//Record the number of the object being// instantiated
objNumber = objCntB;System.out.println(
"In xstr for B, objCntB = " + objCntB);}//end constructor
//-----------------------------------------//private void bShow(){
System.out.println("In bShow, bVar = " + bVar);
System.out.println("In bShow, objNumber = " + objNumber);
//Invoke the private method named aShow// belonging to the internally associated
// object of the class named A.aShow();
}//end bShow//=========================================//
//Note that this class is defined internal to// the class named B.
class C extends X{//member class of Bprivate int cVar;
private A refToA;private B refToB;
private String className = "C";private int objNumber = 0;
C(int val){//constructorcVar = val;
//Instantiate separate objects of the// enclosing classes B and C. Will
// display info about them later. The// object of the Class B is internally
// associated with the original object of// the Class A.
//Increment the object counter in the// top-level class.
A.objCntC++;objNumber = A.objCntC;
System.out.println("In xstr for C, objCntC = "
+ A.objCntC);//Instantiate object of private member
// class named D.new D();
//Instantiate objects of enclosing// classes named A and B.
refToA = new A(10);refToB = new B(20);
}//end constructorpublic void cShow(){
System.out.println("-1-");//separator//Display private member variables
// belonging to this object.System.out.println(
"In cShow, objNumber = " + objNumber);System.out.println("In cShow, cVar = " + cVar);
System.out.println("-2-");//separator//Invoke the private method named bShow
// in the internally associated object of// the class named B. This method will,
// in turn invoke the private method// named aShow in the object of the class
// named A to which the object of the// class named B is internally
// associated.bShow();
System.out.println("-3-");//separator//Invoke the private method named aShow
// in the internally associated object// of the class named A.
aShow();System.out.println("-4-");//separator
//Illustrate the syntax required to gain// access to the objects instantiated
// from the classes named C, B, and A.// The first five statements produce the
// same result. The class names that are// displayed match the names of the class
// files produced by the compilation// process.
System.out.println(getClass().getName());System.out.println(
this.getClass().getName());System.out.println(
C.this.getClass().getName());System.out.println(
B.C.this.getClass().getName());System.out.println(
A.B.C.this.getClass().getName());System.out.println("-5-");//separator
//The following two statements produce// the same output
System.out.println(B.this.getClass().getName());
System.out.println(A.B.this.getClass().getName());
System.out.println("-6-");//separatorSystem.out.println(
A.this.getClass().getName());System.out.println("-7-");
//Display private instance variables and// class names belonging to separate
// objects instantiated from the// enclosing classes named A and B.
System.out.println("In cShow, bVar = " + refToB.bVar);
System.out.println(refToB.getClass().getName());
System.out.println("In cShow, aVar = " + refToA.aVar);
System.out.println(refToA.getClass().getName());
System.out.println("-8-");//Invoke the private bShow method on the
// separate object instantiated from the// class named B in order to show the
// object to which that object is// internally associated. Even though
// this object was instantiated from// within the constructor for the class
// named C, it is internally associated// with the object of the class A that
// was originally used to instantiate the// object of the class named C.
refToB.bShow();System.out.println("-9-");
//Invoke the private aShow method on the// separate object instantiated from the
// class named A.refToA.aShow();
System.out.println("-10-");//Illustrate the inheritance hierarchy to
// which the class named C belongs by// getting and displaying the variable
// named className from both the C class// and the X class. Note that the
// variable is protected in the X class.// Also invoke the overridden toString
// methods belonging to the object// instantiated from the class named C.
// One version is overridden in the class// named X and the other version is
// overridden in the class named C. Note// that the inheritance hierarchy is
// totally independent of the containment// hierarchy.
System.out.println("className = " + className);
System.out.println(toString());//Note: cannot access private variable in
// superclass named X. Must be protected,// package, or public.
System.out.println("className = " + super.className);
System.out.println(super.toString());}//end cShow
//---------------------------------------////Override the toString method
public String toString(){return "toString in Class C";
}//end overridden toString//=======================================//
private class D{//member class of CD(){//constructor
System.out.println("Construct obj of private class D.");
System.out.println(" Private class file name: "
+ this.getClass().getName());}//end constructor
//Note that all four class definitions end// here in the proper nested order.
}//end class D}//end class C
}//end class B}//end class A -end-
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