polyconstructors.java

来自「think in java TIJ-3rd-edition-code.zip」· Java 代码 · 共 41 行

//: c07:PolyConstructors.java
// Constructors and polymorphism
// don't produce what you might expect.
import com.bruceeckel.simpletest.*;

abstract class Glyph {
  abstract void draw();
  Glyph() {
    System.out.println("Glyph() before draw()");
    draw(); 
    System.out.println("Glyph() after draw()");
  }
}

class RoundGlyph extends Glyph {
  int radius = 1;
  RoundGlyph(int r) {
    radius = r;
    System.out.println(
      "RoundGlyph.RoundGlyph(), radius = "
      + radius);
  }
  void draw() { 
    System.out.println(
      "RoundGlyph.draw(), radius = " + radius);
  }
}

public class PolyConstructors {
  public static void main(String[] args) {
    SimpleTest monitor =
      new SimpleTest("PolyConstructors");
    new RoundGlyph(5);
    monitor.expect(new String[] {
      "Glyph() before draw()",
      "RoundGlyph.draw(), radius = 0",
      "Glyph() after draw()",
      "RoundGlyph.RoundGlyph(), radius = 5"
    });
  }
} ///:~