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))；
}
}