求图形面积

class Trangle {
 double sideA,sideB,sideC,length,area;
 boolean boo;
 public Trangle(double a,double b,double c) {
  this.sideA = a;
  this.sideB = b;
  this.sideC = c;
  if(a+b>c&&(a-b<c||b-a<c)) {
   boo = true;
  }
  else {
   boo = false;
  }
 }
 double getLength() {
  return sideA+sideB+sideC;
 }
 public double getArea() {
  if(boo) {
           double p = (sideA+sideB+sideC)/2.0;
           area = Math.sqrt(p*(p-sideA)*(p-sideB)*(p-sideC)) ;
           return area;
          }
          else {
           System.out.println("不是一个三角形，不能计算面积！");
           return 0;
          }
 }
 public void setABC(double a,double b,double c) {
  this.sideA = a;
  this.sideB = b;
  this.sideC = c;
  if(a+b>c&&Math.abs(a-b)<c) {
   boo = true;
  }
  else {
   boo = false;
  }
 }
}

class Lader {
 double above,bottom,height,area;
 Lader(double a,double b,double h) {
  this.above = a;
  this.bottom = b;
  this.height = h;
 }
 double getArea() {
  return  ((above+bottom)*height)/2.0;
 }
}
class Circle {
 double radius,area;
 Circle(double r) {
  this.radius = r;
 }
 double getArea() {
  area = 3.14*radius*radius;
  return area;
 }
 double getLength() {
  return 2*3.14*radius;
 }
 void setRadius(double newRadius) {
   radius = newRadius;
 }
 double getRadius() {
  return radius;
 }
}
class AreaAndLength {
 public static void main(String []args) {
  double length;
  double area = 0;
  Circle circle = null;
  Trangle trangle;
  Lader lader;
  circle = new Circle(1.0);
  trangle = new Trangle(3.0,4.0,5.0); 
        lader = new Lader(3.0,6.0,2.0); 
        length = circle.getLength();
        System.out.println("圆的周长:"+length);
        area = circle.getArea();
        System.out.println("圆的面积:"+area);
        
        length = trangle.getLength();
        System.out.println("三角形的周长:"+length);
        area = trangle.getArea();
        System.out.println("三角形的面积:"+area);
        
        area = lader.getArea();
        System.out.println("梯形的面积:"+area);
        
        trangle.setABC(12,34,1);
        length=trangle.getLength();
        System.out.println("三角形的周长:"+length);
        area =trangle.getArea();
        System.out.println("三角形的面积:"+area);
 }
}