interface CShape // 定義介面 CShape
final double PI=3.14; //final 可省略
public abstract void show(); //public abstract 可省略
class CCircle implementation CShape
public CCircle(double r) //CCircle建構元
public void show() //改寫介面中抽象函數
System.out.println("面積="+PI*radius*radius);
class CRectangle implements CShape
public CRectangle(int w,int h) //CRectangle建構元
System.out.println("area="+width*height);
public static void main(String args[])
CShape shap01,shap02; //透過介面宣告變數
shap01=new CRectangle(5,10);