Polymorphism笔记

package poly;

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

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

class RoundGlyph extends Glyph {
    private 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 PolyConstructor {
    public static void main(String[] args) {
        new RoundGlyph(5);
    }
}

 

【

Glyph() before draw()
RoundGlyph.draw(), radius = 0
Glyph() after draw()
RoundGlyph.RoundGlyph(), radius = 5

】

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不要在构造函数里面调用多态函数，否则会出现意想不到的结果