程序允许您在N维空间中指定点

Question

So here is the gist of the assignment I am having difficulty with:

• Write a java class called Point to represent a N-Dimensional point (With coordinates that are double)

  • The constructor should take any number of coordinates
  • The class should have accessor method for any coordinates
  • Write toString() and copy() and equals() helper methods

  • Keep track of every created poin

  • Write a java class called Line to represent a line (with a starting point and an ending point)

  • The constructor arguments are the start and end points
  • The constructor MUST throw an error when the 2 points are not of the same dimension
  • Write a toString() and copy() and equals() helper method
  • Provide a getLineLength() method - Look up "Euclidian Distance" on wiki
  • Keep track of every created line

So i have created my line and point class but I am not sure if I am creating my line or point class correctly. I already have my main method designed to take input from the console and store that input into two different arrays for the coordinates. When i try to call this method in my main to print the coordinates and distance i get back the output:

The distance between ( 4.0 , 5.0 ) ( 2.0 , 3.0 ) ( 0.0 , 0.0 ) is>

So I was hoping i could get help in clarifying if I am creating my constructor and everything else correctly. Here is my code for both classes thus far:

public class Point{

  private double[] coordinate1;
  private double[] coordinate2;


  public Point(double[] array1, double[] array2){
    this.coordinate1 = array1;
    this.coordinate2 = array2;
  }
  //method to get array inputs and copy them
  public void copy(double[] points1, double[] points2){

    double[] coordinate1 = new double[points1.length +1];
    for(int copyIndex = 0; copyIndex < points1.length; copyIndex++){
      coordinate1[copyIndex] = points1[copyIndex];
    }
    points1 = coordinate1;

    double[] coordinate2 = new double[points2.length +1];
    for(int copyIndex = 0; copyIndex < points2.length; copyIndex++){
      coordinate2[copyIndex] = points2[copyIndex];
    }
    points2 = coordinate2;
  }
  //method to print the coordinates
  public void printArray(){

    double array1 = coordinate1.length;
    double array2 = coordinate2.length;
    for (int i = 0; i < array1 && i < array2; i++) {
      System.out.println("( " + coordinate1[i] + " , " + coordinate2[i] + " ) ");
    }
  }
}


public class Line{

  private double[] coordinate1;
  private double[] coordinate2;
  private double distance;

  public Line(double[] array1, double[] array2){
    this.coordinate1 = array1;
    this.coordinate2 = array2;
  }
  public double getLine(double[] coordinate1, double[] coordinate2){
    double diffSquareSum = 0.0;
    for(int i=0;i<coordinate1.length;i++) {
      diffSquareSum += (coordinate1[i] - coordinate2[i]) * (coordinate1[i] - coordinate2[i]);
    }
    distance = Math.sqrt(diffSquareSum);
    return distance;
  }
  public String toString(){
    return "The distance is " + distance;
  }
}

Please let me know if I need to clarify or expand on my question. Appreciate any help. Thank you. Here is the output expected from the program once ran:

Example:

Enter point # 1 dimension # 1 or "Random" or "Exit" or "Help" or blank line to proceed: 3.14 Enter point # 1 dimension # 2 or "Random" or "Exit" or "Help" or blank line to proceed: 0 Enter point # 1 dimension # 3 or "Random" or "Exit" or "Help" or blank line to proceed:

Enter point # 2 dimension # 1 or "Random" or "Exit" or "Help" or blank line to proceed: 0 Enter point # 2 dimension # 2 or "Random" or "Exit" or "Help" or blank line to proceed: hEl

• This program allows you specify points in N-dimensional space:
  • Each point can have different number of non-zero coordinate
  • You may request a random number for any coordinate by typing "RANDOM"
  • When you are finished entering the cordinate just press the key
• Pairs of point are used to create a lines
  • If the 2 points have mismatched dimensions and error will be shown
  • When a line is created, the line distance is provided
• When you are done specifying points and lines type "EXIT" to display final operation statistics
• All key words are case insensitive and can be abreviated
• Random number will be scaled between -1,000.00 and +1,000.00

Enter point # 2 dimension # 2 or "Random" or "Exit" or "Help" or blank line to proceed: 2.71 Enter point # 2 dimension # 3 or "Random" or "Exit" or "Help" or blank line to proceed: The distance between ( 3.14 , 0.0) and ( 0.0 , 2.71) is 4.147734321289154

Enter point # 1 dimension # 4 or "Random" or "Exit" or "Help" or blank line to proceed: Random --> -75.1234 Enter point # 1 dimension # 5 or "Random" or "Exit" or "Help" or blank line to proceed: Enter point # 2 dimension #1 or "Random" or "Help" or "Exit" or blank line to proceed: RA --> 38.12851983534693 Enter point # 2 dimension #2 or "Random" or "Help" or "Exit" or blank line to proceed: rAnD --> 74.31366638262983

Enter point # 2 dimension #3 or "Random" or "Help" or "Exit" or blank line to proceed: Ouch - You tried to create a line with points of disimilar dimension!

Enter point # 1 dimension # 1 or "Random" or "Exit" or "Help" or blank line to proceed: EXIT

You created 4 points: ( 3.14 , 0.0 ) ( 0.0 , 2.71 ) ( -75.1234 ) ( 38.12851983534693 , 74.31366638262983 ) You created 1 lines: ( 3.14 , 0.0 ) to ( 0.0 , 2.71 ) with length 4.147734321289154

So it keeps asking for coordinate doubles and creates a line and then prints out all lines made once program closes. Hope that helps clarify what the assignment requires

Answer 1

It's not clear why your constructor would have 2 arrays - it seems there should be only 1 array to represent all of the N possible axes.

Also, it's not clear how the coordinates should be passed to the constructor.

Like this using multiple arguments?

public class Point {
    private double[] coordinates;

    public Point(double...coordinates) {
        this.coordinates = coordinates;
    }
}

Or like this using an array?

public class Point {
    private double[] coordinates;

    public Point(double[] coordinates) {
        this.coordinates = coordinates;
    }
}

The copy method should likely have this signature:

Point copy();

so that you return a copy of the current instance.

The requirement for the Line class indicates the constructor takes two Point s so it should look similar to this:

public Line(Point p1, Point p2);

and the methods working with p1 and p2 .

Answer 2

You only need one array to represent each point. The length of the array would tell you the dimension of that point. Your code is basically a hard coded 2D point. Correct usage should look something like this:

double[] coordinate1 = {0.0};// 1d coordinate
double[] coordinate2 = {0.0,1.0};// 2d coordinate
double[] coordinate3 = {0.0,1.0,2.0};// 3d coordinate

Point point1 = new Point(coordinate1);// 1d point
Point point2 = new Point(coordinate2);// 2d point
Point point3 = new Point(coordinate3);// 3d point

int dimension = point1.getCoordinates().length;

Your line class will have two variables of type Point passed in through the constructor. You can make two quick methods

public boolean isSameDimension(Point p1, Point p2)
{
    if(p1.getDimension() == p2.getDimension())
        return true;
    return false;
}

public int getDimension()//In point class
{
    return getCoordinates().length;
}