第六章第十九题（三角形）(Triangles)

第六章第十九题（三角形）(Triangles)

• *6.19（三角形）实现以下两个方法：
  public static boolean isValid(double side1, double side2, double side3)
  public static double area(double side1, double side2, double side3)
  编写一个测试程序，读入三角形三条边的值。使用isValid方法检测输入是否有效，并使用area方法计算面积。如果输入有效，则显示面积，否则显示输入无效。三角形面积计算公式在编程练习题2.19中给出。
  *6.19(Triangles) Implement the following two methods:
  public static boolean isValid(double side1, double side2, double side3)
  public static double area(double side1, double side2, double side3)
  Write a test program that reads three sides for a triangle and uses the isValid method to test if the input is valid and uses the area method to obtain the area. The program displays the area if the input is valid. Otherwise, it displays that the input is invalid. The formula for computing the area of a triangle is given in Programming Exercise 2.19.
• 参考代码：

package chapter06;

import java.util.Scanner;

public class Code_19 {
    
    
    public static void main(String[] args) {
    
    
        Scanner input = new Scanner(System.in);
        System.out.print("Enter side1 of triangle: ");
        double side1 = input.nextDouble();
        System.out.print("Enter side2 of triangle: ");
        double side2 = input.nextDouble();
        System.out.print("Enter side3 of triangle: ");
        double side3 = input.nextDouble();
        if (isValid(side1,side2,side3))
            System.out.println("The area of triangle is " + area(side1,side2,side3));
        else
            System.out.println("The input is invalid");
    }
    public static boolean isValid(double side1,double side2,double side3){
    
    
        if (side1 + side2 > side3 && side1 + side3 > side2 && side2 + side3 > side1)
            return true;
        return false;
    }
    public static double area(double side1,double side2,double side3){
    
    
        double HalfSumLengthSide = (side1 + side2 + side3) / 2;
        double AreaTriangle = Math.pow(HalfSumLengthSide
                *(HalfSumLengthSide - side1)
                *(HalfSumLengthSide - side2)
                *(HalfSumLengthSide - side3), 0.5);
        return AreaTriangle;
    }
}

• 结果显示：

Enter side1 of triangle: 3
Enter side2 of triangle: 4
Enter side3 of triangle: 5
The area of triangle is 6.0

Process finished with exit code 0