import java.util.*;

abstract class GeometricObject{

  private String color;

 private  boolean filled;  

public String getColor()

{   return color;  }

 public void setColor(String color)

{   this.color = color;  }

 public boolean isFilled()

{   return filled;  }  

public void setFilled(boolean filled)

{   this.filled = filled;  }  

public abstract double getArea();

 public abstract double getPerimeter();

}

class Triangle extends GeometricObject{

 private double oneSide;

 private double twoSide;

 private double threeSide;

 public void setOneSide(double oneSide) {   

this.oneSide = oneSide;  

}

 public void setTwoSide(double twoSide)

{   this.twoSide = twoSide;  }

 public void setThreeSide(double threeSide)

{   this.threeSide = threeSide;  }  

public double getArea()

 {  

 double p = (oneSide + twoSide +threeSide) / 2;   return Math.sqrt(p * (p - oneSide) * (p - twoSide) * (p - threeSide) );  

}

 public double getPerimeter()

 {   return oneSide + twoSide + threeSide;  }

 public String toString()

{  return "area = " + getArea() + "  perimeter" + getPerimeter() + "  color = " + getColor() +"  isFalled = " +  isFilled();  }

}

public class title13_1

{

 public static void main(String[] args)

{   Triangle value = http://www.mamicode.com/new Triangle();

System.out.println("请用户输入第一个三角形边:");

  Scanner input = new Scanner(System.in);

  value.setOneSide(input.nextDouble());  

 System.out.println("请用户输入第二个三角形边:");  

 value.setTwoSide(input.nextDouble());   

System.out.println("请用户输入第三个三角形边:");   

value.setThreeSide(input.nextDouble());  

 System.out.println("请用户输入颜色:");  

 value.setColor(input.next());

  System.out.println("请用户输入是否填充:");  

 value.setFilled(input.nextBoolean());  

 System.out.println("最后结果：  " + value.toString());

 }

}

Java语言程序设计（基础篇）第10版 课后习题13.1答案