阅读以下说明和Java程序，将入(n)处的字句写在对应栏内 [说明] 以下程序的功能时三角形、矩形和正方形的面积输出。 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。 [Java程序] public class areatest { public static viod main(string args[]){ Figure[]Figures={ New triangle(2,3,3),new rectangle(5,8),new square(5) }; for(int i=0; i＜Figures.length;i++){ system.out.println(Figures+'area='+Figures.getarea()); } } } public abstract class figure { public abstract double getarea(); } 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 exends (3) { public square(double width){ (4); } public string tostring(){ return'square:width='+width':'; } } public class triangle entends (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 get area(){ double s=(la+lb+lc)/2.0; return math．sqrt(s*(s-la)*(s-lb)*(s-lc)); } }