两个坐标之间的距离

Question

我想要获得坐标之间的距离，并且由于某种原因它似乎不起作用。感恩，如果有人能帮助！

输出：

从A点到B点的距离为0.0。点a 到点b的距离为0.0。从点a到点b的距离为0.0。从点a到点b的距离为0.035。从P1到P2的距离 4.242640687119285从P1到P3的距离12.727922061357855

package GC01; 

public class Point { 
    private final double x; 
    private final double y; 
    private double distance; 

    public Point(){ 
     x=0.0; 
     y=0.0; 
    } 

    public Point(double x, double y) { 
     this.x=x; 
     this.y=y; 
    } 

    public double distanceTo(Point a, Point b) { 
     double dx = a.x - b.x; 
     double dy = a.y - b.y; 
     distance = Math.sqrt(dx*dx + dy*dy); 
     return distance; 
    } 
    public String toString(){ 
     return "The distance from Point a to Point b is " + distance +"."; 
    } 

public static void main(String[] args){ 
    Point p0 = new Point(); 
    Point p1 = new Point(0.0,0.0); 
    Point p2 = new Point(3.0,3.0); 
    Point p3 = new Point(9.0,9.0); 
    System.out.println(p0.toString()); 
    System.out.println(p1.toString()); 
    System.out.println(p2.toString()); 
    System.out.println(p3.toString()); 
    System.out.println("The distance from p1 to p2 is "+p1.distanceTo(p1,p2)); 
    System.out.println("The distance from p1 to p3 is "+p1.distanceTo(p1,p3)); 
} 
} 

Answer 1

一两件事，我看到的是，当你运行你的主，你调用Point.toString（）方法四你做出积分后的时间。当你这样做时，距离变量还没有被设置，因为distanceTo方法没有被调用。

Point p0 = new Point(); 
Point p1 = new Point(0.0,0.0); 
Point p2 = new Point(3.0,3.0); 
Point p3 = new Point(9.0,9.0); 
System.out.println(p0.toString()); 
System.out.println(p1.toString()); 
System.out.println(p2.toString()); 
System.out.println(p3.toString()); 

当这些Point.toString调用发生，distanceTo方法还没有被调用所以距离尚未设置任何这些点。

因为您调用distanceTo方法，所以您会在最后两行输出数字。

Answer 2

这是否适合您？

public class Point { 
    private final double x; 
    private final double y; 

    public Point() { 
     x = 0.0; 
     y = 0.0; 
    } 

    public Point(double x, double y) { 
     this.x = x; 
     this.y = y; 
    } 

    public double distanceTo(Point other) { 
     double dx = other.x - this.x; 
     double dy = other.y - this.y; 
     double distance = Math.sqrt(dx * dx + dy * dy); 
     return distance; 
    } 

    public String toString() { 
     return x + "/" + y; 
    } 

    public static void main(String[] args) { 
     Point p0 = new Point(); 
     Point p1 = new Point(0.0, 0.0); 
     Point p2 = new Point(3.0, 3.0); 
     Point p3 = new Point(9.0, 9.0); 
     System.out.println(p0.toString()); 
     System.out.println(p1.toString()); 
     System.out.println(p2.toString()); 
     System.out.println(p3.toString()); 
     System.out 
       .println("The distance from p1 to p2 is " + p1.distanceTo(p2)); 
     System.out 
       .println("The distance from p1 to p3 is " + p1.distanceTo(p3)); 
    } 
} 

我从你的类删除distance变量，因为只能有一个点和彼此之间的距离;一个点本身没有距离。

我也改变了distanceTo：当您拨打p1.distanceTo(p2)时，您将p2的参考号传递给p1。 p2现在在distanceTo方法中被称为other。

写作this.x只是一种更详细的写作方式，只是写作x。我想表明这x变量属于distanceTo方法（在这种情况下为p1）的接收方。

最后我改变了toString，以便它打印你的点的X和Y坐标。在Java实例变量，如除去distance总是以0初始化这就是为什么px.toString()总是打印

从点A到点B的距离为0.0

。