43 lines
994 B
Java
43 lines
994 B
Java
// polymorphism/RTTI.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
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// Downcasting & Runtime type information (RTTI)
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// {ThrowsException}
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class Useful {
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public void f() {}
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public void g() {}
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}
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class MoreUseful extends Useful {
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@Override
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public void f() {}
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@Override
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public void g() {}
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public void u() {}
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public void v() {}
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public void w() {}
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}
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public class RTTI {
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public static void main(String[] args) {
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Useful[] x = {
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new Useful(),
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new MoreUseful()
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};
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x[0].f();
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x[1].g();
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// Compile time: method not found in Useful:
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//- x[1].u();
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((MoreUseful)x[1]).u(); // Downcast/RTTI
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((MoreUseful)x[0]).u(); // Exception thrown
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}
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}
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/* Output:
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___[ Error Output ]___
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Exception in thread "main" java.lang.ClassCastException:
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Useful cannot be cast to MoreUseful
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at RTTI.main(RTTI.java:31)
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*/
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