package?com.imooc;
public?abstract?class?Shape{
????public?abstract?double?perimeter();
????public?abstract?double?area();
}
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package?com.imooc;
public?class?Circle?extends?Shape{
????double?r?=?3.4;
????@Override
????public?double?perimeter(){
????retrun?Math.PI?*?2?*?r
????}
????@Override
????public?double?area(){
????return?Math.PI?*?r?*?r;
????}
}
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package?com.imooc;
public?class?initial{
????public?static?void?main(String[]?args){
????Shape?cc?=?new?Circle();
????Shape?rt?=?new?Rectangle();
????System.out.println("圓的面積為："+cc.area());
????System.out.println("圓的周長為："+cc.perimeter());
????}
}