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== Class Casting Demo ==



<source lang="java">

/*
* Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
* cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
* pioneering role in inventing and promulgating (and standardizing) the Java
* language and environment is gratefully acknowledged.
*
* The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
* inventing predecessor languages C and C++ is also gratefully acknowledged.
*/

/** Class Casting Demo. */
public class ClassCast {
public static void main(String[] argv) {
CCA anA = new CCA();
CCB aB = new CCB(1);
CCC aC = new CCC(2,3);
System.out.println("A = " + anA);
System.out.println("B = " + aB);
System.out.println("C = " + aC);
CCA aCast = aC;
System.out.println("aCast = " + aCast);
CCC anotherC = (CCC) aCast;
System.out.println("anotherC = " + anotherC);
}
}
class CCA {
}
class CCB extends CCA {
int one;
CCB(int i) {
one = i;
}
public String toString() {
return "In a B object: " + one;
}
}
class CCC extends CCB {
int two;
CCC(int i, int j) {
super(i); // does "one = i" for us.
two = j;
}
public String toString() {
return "In a C object: " + one + "," + two;
}
}

</source>



== Downcasting and Run-Time Type Identification (RTTI) ==



<source lang="java">

// : c07:RTTI.java
// Downcasting & Run-Time Type Identification (RTTI).
// {ThrowsException}
// From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002
// www.BruceEckel.ru. See copyright notice in CopyRight.txt.
class Useful {
public void f() {
}
public void g() {
}
}
class MoreUseful extends Useful {
public void f() {
}
public void g() {
}
public void u() {
}
public void v() {
}
public void w() {
}
}
public class RTTI {
public static void main(String[] args) {
Useful[] x = { new Useful(), new MoreUseful() };
x[0].f();
x[1].g();
// Compile time: method not found in Useful:
//! x[1].u();
((MoreUseful) x[1]).u(); // Downcast/RTTI
((MoreUseful) x[0]).u(); // Exception thrown
}
} ///:~

</source>

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Admin: 1 версия

в 18:01, 31 мая 2010