Downcasting and Run-Time Type Identification (RTTI) : Polymorphism « Class Definition « Java Tutorial

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Java Tutorial » Class Definition » Polymorphism 
5. 24. 3. Downcasting and Run-Time Type Identification (RTTI)
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 MainClass {
  public static void main(String[] args) {
    Useful[] x = { new Useful(), new MoreUseful() };
    x[0].f();
    x[1].g();

    // x[1].u();
    ((MoreUseful) x[1]).u(); // Downcast/RTTI
    ((MoreUseful) x[0]).u(); // Exception thrown
  }
}
5. 24. Polymorphism
5. 24. 1. Polymorphism
5. 24. 2. An example of polymorphism
5. 24. 3. Downcasting and Run-Time Type Identification (RTTI)
5. 24. 4. Constructors and polymorphism don't produce what you might expect
5. 24. 5. Dynamic Method Dispatch
5. 24. 6. Using run-time polymorphism.
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