子類:public?class?ShapeCircle?extends?Shape

{

protected?double?r;

public?ShapeCircle()

{

setside(0.0);

}

public?ShapeCircle(double?r)

{

setside(r);

}

public?void?setside(double?r)

{

this.r=r;

}

public?double?perimeter()

{

return?Math.PI*2*r;

}

public?String?getType()

{

return?"Circle";

}

}

父類:

import?ShapeCircle;

import?Shape;

public?class?Myshape

{

private?static?ShapeCircle?sc=new?ShapeCircle(4);

private?static?Shape?shapej=new?ShapeCircle(5);

public?static?void?main(String?args[])

{

System.out.println(sc.getType()+","+sc.perimeter());

}

shapej=sc;

System.out.println(shape.getType()+","+shape.perimeter());

}

當編譯到shapej=sc總報錯.為什么,請高手指教.

|

public?static?void?main(String?args[])

{

System.out.println(sc.getType()+","+sc.perimeter());

shapej=sc;

System.out.println(shapej.getType()+","+shapej.perimeter());

}

|

你的語句不能直接寫在類里，如果寫的話可寫為

static?{

shapej=sc;

System.out.println(shape.getType()+","+shape.perimeter());

}

或者寫成：　karma(無為)的方式

|

I?guess?dongjh?forgot?to?put?}?after

System.out.println(shape.getType()+","+shape.perimeter());

總結

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