复制数组并根据它进行

Question

我之前问过一个关于克隆数组的问题，以便在更改区域/缩放多边形等时它不会更改数组的值（封装的基础知识）。 在尝试将数组复制到另一个数组中，使用克隆数组或使用数组列表后，我仍然遇到问题。任何人有任何建议如何复制我的数组，以便我可以对其进行更改，返回方法中的值，但仍然保持传递给构造函数的原始数组的完整性？ Point类定义了传入的值。我也将其发布。多边形创建了大多数这些方法。失意...

public class Point { 

private double x; 
private double y; 

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

public double getX() { 
    return x; 
} 

public double getY() { 
    return y; 
} 

public Point translate(double dx, double dy) { 
    return new Point(x+dx, y+dy); 
} 

public double distanceTo(Point p) { 
    return Math.sqrt((p.x - x)*(p.x -x) + (p.y-y)*(p.y-y)); 
} 

}

import java.util.ArrayList; 
import java.util.Iterator; 
import java.util.List; 

public class PolygonImpl implements Polygon { 

    private double xSum=0; 
    private double ySum=0; 
    private Point[] points; 
    private Point[] cloneList; 
    private Point a; 

    public PolygonImpl(Point[] points) { 
this.points = new Point[points.length]; 
for (int i = 0; i < points.length; i++) 
this.points[i] = points[i]; 
} 



public Point getVertexAverage() { 
    double xSum = 0; 
    double ySum = 0; 
    for (int index = 0; index < points.length; index++) { 
     xSum = xSum + points[index].getX(); 
     ySum = ySum + points[index].getY(); 
     } 

    return new Point(xSum/getNumSides(), ySum/getNumSides()); 
} 

public int getNumSides() { 
    return points.length; 
} 

public void move(Point c) { 
    Point a = getCentroid(); 
    Point newCentroid = new Point(a.getX()+ c.getX(), a.getY() +c.getY()); 


} 

public void scale(double factor) { 
    for (int index = 0; index < points.length; index++) 
    { 
     double x = points[index].getX() *factor; 
     double y = points[index].getY() * factor; 
     Point a = new Point(x,y); 
     points[index] = a; 

    } 
} 




public Point[] getPoints() { 
    // Point[] newPoints = new Point[0]; 
    //for (int i = 0; i <newPoints.length; i++) 
    //{ 
    // newPoints = points.get(i); 
    //} 
    return points; 

} 




public Rectangle getBoundingBox() { 
    double minX= 99999; 
    double maxX= -999999; 
    double minY= 999999; 
    double maxY= -999999; 

    for (int i = 1; i<points.length; i ++){ 
     if (points[i].getX()< minX) 
     { 
      minX= points[i].getX(); 
     } 
     if (points[i].getX() > maxX) 
     { 
      maxX= points[i].getX(); 
     } 
     if (points[i].getY()< minY) 
     { 
      minY= points[i].getY(); 
     } 
     if (points[i].getY() > maxY) 
     { 
      maxY= points[i].getY(); 
     } 

     Point a = new Point(minX, minY); 
     Point b = new Point(maxX, maxY); 
     //need for next three cases 
    } 
    return null; 
      //new Rectangle(Point a, Point b); 
} 




public Point getCentroid() { 
    double x = 0; 
    double y =0; 
    double something = 1/(6*getArea()); 
    for (int i = 0; i< points.length-1; i++) 
    { 
     x+= (points[i].getX() + points[i+1].getX())*(points[i].getX()*points[i+1].getY()-points[i+1].getX()*points[i].getY()); 
     y+= (points[i].getY() + points[i+1].getY())*(points[i].getX()*points[i+1].getY()-points[i+1].getX()*points[i].getY()); 
    } 
     x = x*something; 
     y= y*something; 

    Point a = new Point(x,y); 
    return a; 
} 




public double getArea() { 
    double area = 0; 
for (int i = 0; i <points.length-1; i++){ 
    area += points[i].getX()*points[i+1].getY() - points[i+1].getX()*points[i].getY(); 
} 
    area = area/2; 
return area; 
} 




public void move(double dx, double dy) { 
    //ArrayList<Point> points = new ArrayList<Point>(); 

    for (int index = 0; index < points.length; index++) { 
     { double x = points[index].getX()+dx; 
      double y = points[index].getY()+dy; 
      Point a = new Point(x,y); 

     } 
} 










} 
} 

Answer 1

我不知道，你要克隆你的阵列;然而，我相信你试过类似：

// This won't work because you keep the same reference to the old objects 
public Point[] cloneArrayOfPoints(Point[] points) { 
    Point[] result = new Point[points.length]; 
    for (int i = 0; i < points.length; i++){ 
     result.points[i] = points[i]; 
    } 
    return result; 
} 

但是，你应该试试这个：

// This will work because you create new objects with same old values 
public Point[] cloneArrayOfPoints(Point[] points) { 
    Point[] result = new Point[points.length]; 
    for (int i = 0; i < points.length; i++){ 
     result.points[i] = new Point(points[i].getX(), points[i].getY()); 
    } 
    return result; 
}