Mega Code Archive
Downcasting and Run-Time Type Identification (RTTI)
<![CDATA[
// : c07:RTTI.java
// Downcasting & Run-Time Type Identification (RTTI).
// {ThrowsException}
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. 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
}
} ///:~
]]>