代码运行结果显示最后的几个函数体未定义：trangle() is undefined,要怎么改，遇到类似的问题该怎么改正？

Question

class Trangle{ double sideA,sideB,sideC,area,length; boolean boo; public Trangle(double a,double b,double c) {      this.sideA=a;         this.sideB=b;         this.sideC=c;    if(this.sideA+this.sideB>this.sideC&&this.sideA+this.sideC>this.sideB&&this.sideB+this.sideC>this.sideA) {  this.boo=true;   } else {  this.boo=false;   } return boo; }public double getLength(){  if(this.sideA+this.sideB>this.sideC&&this.sideA+this.sideC>this.sideB&&this.sideB+this.sideC>this.sideA)  {   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(this.sideA+this.sideB>this.sideC&&this.sideA+this.sideC>this.sideB&&this.sideB+this.sideC>this.sideA)    {      this.boo=true;    }    else    {     this.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;   }public double getArea(){  this.area=(this.above+this.bottom)*this.height/2;  return this.area; } } public class AreaAndLength { public static void main(String[] args) {double length,area;Trangle trangle=null;Lader lader;trangle=new Trangle();lader=new Lader();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);area=trangle.getArea();System.out.println("三角形的面积："+area);length=trangle.getLength();System.out.println("三角形的周长："+length);}}class Trangle{ double sideA,sideB,sideC,area,length; boolean boo; public Trangle(double a,double b,double c) {      this.sideA=a;         this.sideB=b;         this.sideC=c;    if(this.sideA+this.sideB>this.sideC&&this.sideA+this.sideC>this.sideB&&this.sideB+this.sideC>this.sideA) {  this.boo=true;   } else {  this.boo=false;   } return boo; }public double getLength(){  if(this.sideA+this.sideB>this.sideC&&this.sideA+this.sideC>this.sideB&&this.sideB+this.sideC>this.sideA)  {   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(this.sideA+this.sideB>this.sideC&&this.sideA+this.sideC>this.sideB&&this.sideB+this.sideC>this.sideA)    {      this.boo=true;    }    else    {     this.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;   }public double getArea(){  this.area=(this.above+this.bottom)*this.height/2;  return this.area; } } public class AreaAndLength { public static void main(String[] args) {double length,area;Trangle trangle=null;Lader lader;trangle=new Trangle();lader=new Lader();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);area=trangle.getArea();System.out.println("三角形的面积："+area);length=trangle.getLength();System.out.println("三角形的周长："+length);}}

Answer 1

查看编译器的报错提示 查找代码的错误

Trangle和Lader两个类中有构造方法 需要传入参数才可以：

trangle=new Trangle(1.0,2.0,3.0);
lader=new Lader(1.0,2.0,3.0);

getArea你定义在Lader类中了 但却在trangle对象上调用的 当然找不到