很菜的方法
import java.util.Scanner; import java.text.DecimalFormat; public class Main { public static void main(String[] args) { Scanner s=new Scanner(System.in); Rectangle r1=new Rectangle(); Square s2=new Square(); Circle c=new Circle(); r1.juLong=s.nextDouble(); r1.juWide=s.nextDouble(); if(r1.juWide!=r1.juLong){ double q= r1.GetArea(r1.juLong, r1.juWide); if (((int)q * 1000) == (int) (q * 1000)){ System.out.println((int)q); }else if(q*10!=(int)q*10){ System.out.println(String.format("%.2f", q)); }else System.out.println(String.format("%.1f", q)); }else{ s2.zr= r1.juLong; double w= s2.GetArea(s2.zr); System.out.println((int)w); } c.r=s.nextDouble(); double e=c.cArea(c.r); if (((int) e * 1000) == (int) (e * 1000)) { System.out.println((int)e); }else if (e*10!=(int)(e*10)){ System.out.println(String.format("%.2f", e)); }else System.out.println(String.format("%.1f", e)); s2.zr=s.nextDouble(); double t= s2.GetArea(s2.zr); if (((int) t * 1000) == (int) (t * 1000)){ System.out.println((int)t); }else if(t*10!=(int)t*10){ System.out.println(String.format("%.2f",t)); }else System.out.println(String.format("%.1f", t)); } } class Square extends Rectangle{ double zr; public double GetArea(double zr) { double sz=zr*zr; return sz; } } class shape { public double GetArea(double l,double w){ double s=l*w; return s; } } class Circle extends shape{ double r; public double cArea(double r){ double s=3.14*r*r; return s; } } class Rectangle extends shape { double juLong; double juWide; }