Printing and comparing array data in java

Question

I recently started learning Java and I'm having some trouble understanding how to make arrays to work the way I want them to. Here I have an assignment of creating a polygon class with different methods inside. Basically the class represents a convex polygon in a plane. The array receives user input that consists of x and y coordinates and places them inside. (max number of vertices is 10). There are some functions that I have no idea how to do and I would really appreciate some help with. Point Class - which is used to get coordinates

public class Point {
  private double _x;
  
  private double _y;
  
  public Point() {
    this._x = 0.0D;
    this._y = 0.0D;
  }
  
  public Point(double x, double y) {
    this._x = x;
    this._y = y;
  }
  
  public Point(Point other) {
    this._x = other._x;
    this._y = other._y;
  }
  
  public double getX() {
    return this._x;
  }
  
  public double getY() {
    return this._y;
  }
  
  public void setX(double x) {
    if (x >= 0.0D)
      this._x = x; 
  }
  
  public void setY(double y) {
    if (y >= 0.0D)
      this._y = y; 
  }
  
  public boolean isAbove(Point other) {
    return (this._y > other._y);
  }
  
  public boolean isUnder(Point other) {
    return other.isAbove(this);
  }
  
  public boolean isLeft(Point other) {
    return (this._x < other._x);
  }
  
  public boolean isRight(Point other) {
    return other.isLeft(this);
  }
  
  public double distance(Point other) {
    double distance = Math.sqrt(Math.pow(this._x - other._x, 2.0D) + Math.pow(this._y - other._y, 2.0D));
    return distance;
  }
  
  public void move(double dx, double dy) {
    double x = this._x + dx;
    double y = this._y + dy;
    if (x >= 0.0D && y >= 0.0D) {
      this._x = x;
      this._y = y;
    } 
  }
  
  public boolean equals(Point other) {
    return (this._x == other._x && this._y == other._y);
  }
  
  public String toString() {
    return "(" + this._x + "," + this._y + ")";
  }
}

Polygon Class - main class im working on

/**
 * Write a description of class Polygon here.
 *
 * @author [REDACTED]
 * @version (Ver 1.0)
 */
public class Polygon {
    private Point[] _vertices;
    private int _noOfVertices;
 
    public Polygon() {
        _vertices = (Point[]) new Point[10];
        _noOfVertices = 0;
    }
 
    public Polygon(Point[] arr) {
        _vertices = (Point[]) new Point[10];
        _noOfVertices = 0;
 
        if (arr.length > 10) {
            return;
        }
        // for (Point P : arr)
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] != null) {
                _vertices[i] = arr[i];
                _noOfVertices++;
            }
        }
 
    }
 
    public boolean addVertex(double x, double y) {
        if (_noOfVertices >= 10)
            return false;
 
        Point p = new Point(x, y);
        _vertices[_noOfVertices] = p;
        _noOfVertices++;
        return true;
    }
 
    public Point highestVertex() {
    for (int i = 0; i < _noOfVertices; i++) {
    
        
    }
 
    }
 
    public String toString() {
    
    
    }
 
    public double calcPerimeter() {
    for (int i = 0; i < arr.length; i++) {
        
    }
 
    }
 
    public double caclArea() {
     Point ppp = _vertices[zzz]
    }
 
    public boolean isBigger(Polygon other) {
 
    }
 
    public int findVertex(Point p) {
        for (int i = 0; i < _noOfVertices; i++) {
            if (p.equals(_vertices[i])) {
                return i;
            }
        }
        return -1;
    }
 
    public Point getNextVertex(Point p) {
 
        for (int i = 0; i < _noOfVertices; i++) {
            if (p.equals(_vertices[i])) {
                if (i == _noOfVertices - 1) {
                    return new Point(_vertices[0]);
                }
                return new Point(_vertices[i + 1]);
 
            }
        }
        return null;
    }
 
    public Polygon getBoundingBox() {
 
    }
}

I have no idea how to do these functions: Line 44: public Point highestVertex() {} - returns a copy of the highest point in the polygon. If there is more than one vertice at the same Y - the method will return the first one it encountered (with the said Y) If there are no vertices aka the array is empty it will return null. Line 52: public String toString() {} - method that returns a string of points representing the polygon. The string should be in the following format: The polygon has 5 vertices: ((2.0,1.0),(5.0,0.0),(7.0,5.0),(4.0,6.0),(1.0,4,0)) If there are no vertices the method will return a string in the following format: The polygon has 0 vertices.

English is not my first language so I apologize for any grammar mistakes in advance.

Answer 1

First, it's not really the best to ask homework questions here, this is a concept that you should learn.

In highestVertex(), they outline the 3 cases for you: 1st case: If point-y is equal to another point-y, return the first vertex that has point-y. 2nd case: if arr has no elements return null. 3rd case: in loop, check each element's y value in the array and compare it to the biggest y so far. Use this line before your loop:

int max = Integer.MIN_VALUE;

Inside loop:

if (arr[i] > max) max = arr[i]

For toString(), again loop throughout the array, and add each point to a tracker string that you will return.

String str = "";

loop

str += arr[i].toString() + ",";

This works except you need to loop until arr's second to last element, as you will have an extraneous comma after the last point.