【求解】已知三角形各点坐标，求三角形面积。
各位大神，以下是我求三角形面积的代码，还请大神们看看哪里错了，我输入坐标后，最后结果都显示为1.0，神奇了。
import java.util.*;
class MyClass{
public static void main(String args[]){
Scanner input = new Scanner(System.in);
System.out.print("Please enter the pixel:");
double x1 = input.nextDouble();
double y1 = input.nextDouble();
double x2 = input.nextDouble();
double y2 = input.nextDouble();
double x3 = input.nextDouble();
double y3 = input.nextDouble();
double side1 =Math.pow((Math.pow((x1-x2), 2)+Math.pow((y1-y2),2)),1/2);
double side2 =Math.pow((Math.pow((x2-x3), 2)+Math.pow((y2-y3),2)),1/2);
double side3 =Math.pow((Math.pow((x3-x1), 2)+Math.pow((y3-y1),2)),1/2);
double s =(side1 + side2 + side3)/2;
double area =Math.pow((s*(s-side1)*(s-side2)*(s-side3)),1/2);
System.out.println("The triangle area ia " + area);
}
}
[最优解释]
1 Math 类里pow()的定义，public static double pow(double a,double b)，要求传入的参数是double型的。
2 double side1 =Math.pow((Math.pow((x1-x2), 2)+Math.pow((y1-y2),2)),1/2);
看这语句，x1,x2,y1,y1都是double的，int 型字面量“2”转型为double 是2.0.
3 关键是那个 1/2，这个转换过程是 1 2都是int型字面量，程序先按整型计算1/2，结果是0，之后把这个0 转
成double型，结果是0.0.
4 所以楼主的代码相当于：
double side1 =Math.pow((Math.pow((x1-x2), 2)+Math.pow((y1-y2),2)),0);
算下来：
三个边都是1。
后面的计算面积的代码：
double area =Math.pow((s*(s-side1)*(s-side2)*(s-side3)),1/2);
相当于：
double area =Math.pow((s*(s-side1)*(s-side2)*(s-side3)),0);
所以这个area=1.0.
试试下面的代码：
import java.util.*;
public class CalculateTheAreaOfTriangle1
{
public static void main(String args[])
{
Scanner input = new Scanner(System.in);
System.out.println("Please enter the pixel:");
double x1 = input.nextDouble();
double y1 = input.nextDouble();
double x2 = input.nextDouble();
double y2 = input.nextDouble();
double x3 = input.nextDouble();
double y3 = input.nextDouble();
double side1 =Math.pow((Math.pow((x1-x2), 2)+Math.pow((y1-y2),2)),1/2);
System.out.println("side 1 is "+side1);
double side2 =Math.pow((Math.pow((x2-x3), 2)+Math.pow((y2-y3),2)),1/2);
System.out.println("side 2 is "+side2);
double side3 =Math.pow((Math.pow((x3-x1), 2)+Math.pow((y3-y1),2)),1/2);
System.out.println("side 3 is "+side3);
double s =(side1 + side2 + side3)/2;
double area =Math.pow((s*(s-side1)*(s-side2)*(s-side3)),1/2);
System.out.println("The triangle area is " + area);
side1 =Math.pow((Math.pow((x1-x2), 2)+Math.pow((y1-y2),2)),1.0/2);//1/2 变成1.0/2或者(double)1/2)
System.out.println("side 1 is "+side1);
side2 =Math.pow((Math.pow((x2-x3), 2)+Math.pow((y2-y3),2)),1.0/2);
System.out.println("side 2 is "+side2);
side3 =Math.pow((Math.pow((x3-x1), 2)+Math.pow((y3-y1),2)),1.0/2);
System.out.println("side 3 is "+side3);
s =(side1 + side2 + side3)/2;
area =Math.pow((s*(s-side1)*(s-side2)*(s-side3)),1.0/2);
System.out.println("The triangle area is " + area);
//看看下面的输出。
//
double test=1/2;
System.out.println("test is" +test);
double test1=1.0/2;
System.out.println("test1 is" +test1);
}
}
double side1 =Math.pow((Math.pow((x1-x2), 2)+Math.pow((y1-y2),2)),1/2);
double side1 =Math.pow((Math.pow((x1-x2), 2)+Math.pow((y1-y2),2)),（double)1/2);
