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请大家帮帮忙,看看这个程序的允许结果为什么是这个?想了好久都不清楚

摘要: 请大家帮帮忙,看看这个程序的允许结果为什么是这个?想了好久都不清楚

import java.io.*;
import static java.lang.Math.sqrt;
public class TryGeometry
{
public static void main(String[] args)
{
Point start = new Point(0.0,1.0);
Point end = new Point(5.0,6.0);

System.out.println("Points created are "+start+" and "+end);

Line line1 = new Line(start,end);
Line line2 = new Line(0.0,3.0,3.0,0.0);
System.out.println("Lines created are "+line1+" and "+line2);

System.out.println("Intersection is "+line2.intersects(line1));

end.move(1.0,-5.0);
System.out.println("Intersection is "+line1.intersects(line2));
}
}

class Point
{
double x;
double y;

Point(double xVal,double yVal)
{
x = xVal;
y = yVal;
}

Point(final Point oldPoint)
{
x = oldPoint.x;
y = oldPoint.y;
}

void move(double xDelta,double yDelta)
{
x += xDelta;
y += yDelta;
}

double distance(final Point aPoint)
{
return sqrt((x - aPoint.x)*(x - aPoint.x)+(y - aPoint.y)*(y - aPoint.y));
}

public String toString()
{
return Double.toString(x) + ", "+y;
}
}

class Line
{
Point start;
Point end;

Line(final Point start,final Point end)
{
this.start = new Point(start);
this.end = new Point(end);
}

Line(double xStart,double yStart,double xEnd,double yEnd)
{
start = new Point(xStart,yStart);
end = new Point(xEnd,yEnd);
}

double length()
{
return start.distance(end);
}

public String toString()
{
return "("+start+"):("+end+")";
}

Point intersects(final Line line1)
{
Point localPoint = new Point(0,0);
double num = (this.end.y - this.start.y)*(this.start.x - line1.start.x) -
(this.end.x - this.start.x)*(this.start.y - line1.start.y);

double denom = (this.end.y - this.start.y)*(line1.end.x - line1.start.x) -
(this.end.x - this.start.x)*(line1.end.y - line1.start.y);

localPoint.x = line1.start.x + (line1.end.x - line1.start.x)*num/denom;
localPoint.y = line1.start.y + (line1.end.y - line1.start.y)*num/denom;

return localPoint;
}
}
-------------------------------------------------------------------------
Intersection is:1.0 , 2.0 我计算得到的却是1.0 , 1.2

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开始：你line1的两点是(0,1),(5,6),直线是y=x+1;line2的两点是(0,3),(3,0)直线是x+y=3;
交点是(1,2)啊
后来，line1的直线变成乐y=1;line2没有变，所以交点是(2,1)

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能不能再说详细一点

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改成这样
Line(final Point start,final Point end)
{
this.start = start;
this.end = end;
}

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如果照楼主的那样
那么end.move()没有改变直线

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怎么楼主的程序我编译时有错误呢？
sqrt 这个好象有问题？难道是我JDK不支持

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Points created are 0.0, 1.0 and 5.0, 6.0
Lines created are (0.0, 1.0):(5.0, 6.0) and (0.0, 3.0):(3.0, 0.0)
Intersection is 1.0, 2.0
Intersection is 1.0, 2.0

我这结果

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