阅读以下说明和Java源程序，将应填入(n)处的字句写在答题纸的对应栏内。

说明

以下程序的功能是计算三角形、矩形和正方形的面积并输出。

程序由5个类组成：AreaTest是主类，类Triangle、Rectangle和Square分别表示三角形、矩形和正方形，抽象类Figure提供了一个计算面积的抽象方法。

程序

public class AreaTest{

public static void main(String args[]){

Figure[]figures={

new Triangle(2,3,3)，new Rectangle(5,8)， new Square(5)

}；

for(int i=0；i＜figures．1ength；i++){

System.out.println(figures[i]+"area="+figures[i]．getArea())；

}

}

}

public abstract class Figure{

public abstract double SetAJea()；

public class Rectangle extends (1) {

double height;

double width;

public Rectangle(double height,double width){

this.height=height;

this.width=width;

}

public String toString(){

return "Rectangle:height="+height+",width="+width+":";

}

public double getArea() { return (2);

} } public class Square extends (3) {

public Square(double width) {

(4);

}

public String toString() {

return "Square:width="+width+":";

} } public class Triangle extends (5). {

double la;

double lb;

double lc;

public Triangle(double la,double lb,double lc) {

this.la=la; this.lb=lb; this.lc=lc;

public String toString(){

return "Triangle: sides="+la+","+lb+","+lc+":";

public double getArea() {

double s=(la+lb+lc)/2.0;

return Math.sqrt(s*(s-la)*(s-lb)*(s?1c))；

}

}