finaloverridingillusion.java

经典java书籍《thinking in java（第三版）》的源码

//: c06:FinalOverridingIllusion.java
// It only looks like you can override
// a private or private final method.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
import com.bruceeckel.simpletest.*;

class WithFinals {
  // Identical to "private" alone:
  private final void f() {
    System.out.println("WithFinals.f()");
  }
  // Also automatically "final":
  private void g() {
    System.out.println("WithFinals.g()");
  }
}

class OverridingPrivate extends WithFinals {
  private final void f() {
    System.out.println("OverridingPrivate.f()");
  }
  private void g() {
    System.out.println("OverridingPrivate.g()");
  }
}

class OverridingPrivate2 extends OverridingPrivate {
  public final void f() {
    System.out.println("OverridingPrivate2.f()");
  }
  public void g() {
    System.out.println("OverridingPrivate2.g()");
  }
}

public class FinalOverridingIllusion {
  private static Test monitor = new Test();
  public static void main(String[] args) {
    OverridingPrivate2 op2 = new OverridingPrivate2();
    op2.f();
    op2.g();
    // You can upcast:
    OverridingPrivate op = op2;
    // But you can't call the methods:
    //! op.f();
    //! op.g();
    // Same here:
    WithFinals wf = op2;
    //! wf.f();
    //! wf.g();
    monitor.expect(new String[] {
      "OverridingPrivate2.f()",
      "OverridingPrivate2.g()"
    });
  }
} ///:~