好。我已经尝试了一切，而且我一直在寻找互联网上的答案，包括这个网站，但是......根本没有运气。
这是我的代码：
package com.exercises.algorithms;
import java.awt.*;
public class Points2DN {
private Point[] points;
protected int[] closestPoints = new int[2];
private double distance;
Points2DN(int n) {
this.points = new Point[n];
for (int i = 0; i < n; i++) {
this.points[i].x = (int) Math.floor(Math.random()*100);
this.points[i].y = (int) Math.floor(Math.random()*100);
System.out.println("Test: " + points[i].x + "," + points[i].y + "\n");
System.out.println("OK");
}
this.distances(this);
}
public static void imprimePuntos(Point[] arrayPuntos) {
for (int i = 0; i < arrayPuntos.length; i++) {
System.out.println("Punto " +(i+1) + ": " + "( "
+ arrayPuntos[i].x + " , "
+ arrayPuntos[i].y + " )");
}
}
public static void printClosest(Points2DN puntos) {
System.out.println("\nLos puntos más cercanos son: ");
System.out.println("Puntos: \t"
+ (puntos.points[puntos.closestPoints[0]]).toString() + " "
+ (puntos.points[puntos.closestPoints[1]]).toString());
System.out.println("Distancia: " + puntos.distance);
}
private void distances(Points2DN puntos) {
for (int i = 0; i < puntos.points.length; i++) {
// Iterative loop for the other points to be check with
for (int j = (i+1); j < this.points.length; j++) {
if (i == 0 && j == 1) {
int p = puntos.closestPoints[0] = i;
int q = puntos.closestPoints[1] = j;
puntos.distance = (puntos.points[p]).distance(puntos.points[q]);
continue;
}
double distancePair = puntos.points[i].distance(puntos.points[j]);
if (distancePair < puntos.distance){
puntos.closestPoints[0] = i;
puntos.closestPoints[1] = j;
puntos.distance = distancePair;
}
}
}
}
public static void main(String[] args) {
try {
int numberOfPoints = Integer.parseInt(args[0]);
if (args.length == 1) {
System.out.println("Calculando...");
Points2DN puntos = new Points2DN(numberOfPoints);
imprimePuntos(puntos.points);
printClosest(puntos);
}
else {
// Nothing
}
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Not a valid number of points");
} catch (Exception e) {
System.out.println(e.toString());
}
}
}
问题发生在下面片段的最后一行，，在尝试使用数组中的一个Point对象＆＃34; points＆＃34;之后。他们应该填充＆＃34; int＆＃34;在（x，y）上键入值（0,0），并进行初始化。我用尺寸检查了尺码：
points.length
结果是我在IDE上设置为运行项目的参数。例如，如果＆＃39; n＆＃39;是10，那个值是10。这没关系，所以...为什么地狱不起作用！??
Points2DN(int n) {
this.points = new Point[n];
for (int i = 0; i < n; i++) {
this.points[i].x = (int) Math.floor(Math.random()*100);
答案 0 :(得分：5)
new Point[n]创建一个Point的数组，但它不会创建任何实际的Point个对象来放在该数组中。这就像购买一个可以存放书籍的盒子一样 - 除非你把书放在那里，否则它实际上不会有任何书籍。
您需要为要使用的每个索引元素创建Point，例如：
for (int i = 0; i < n; i++) {
points[i] = new Point();
points[i].x = (int) Math.floor(Math.random()*100);
...
答案 1 :(得分：0)
按照yshavit的建议，并修改了一些代码，这就是结束的方式。
/*
* Points2DN - Algorithms to calculate distance in 2D
*
* Author:
* @Ruyman
*/
package com.exercises.algorithms;
import java.awt.*;
// import java.util.*;
import java.math.BigDecimal;
import java.math.RoundingMode;
public class Points2DN {
private Point[] points;
protected int[] closestPoints = new int[2];
private BigDecimal distance;
Points2DN(int n) {
this.points = new Point[n];
for (int i = 0; i < n; i++) {
this.points[i] = new Point();
this.points[i].x = (int) Math.floor(Math.random()*100);
this.points[i].y = (int) Math.floor(Math.random()*100);
}
this.distances(this);
}
Points2DN(int n, int x) {
this.points = new Point[n];
for (int i = 0; i < n; i++) {
this.points[i] = new Point();
this.points[i].x = (int) Math.floor(Math.random()*100);
this.points[i].y = (int) Math.floor(Math.random()*100);
}
this.distances(this, x);
}
public static void imprimePuntos(Point[] arrayPuntos) {
for (int i = 0; i < arrayPuntos.length; i++) {
System.out.println("Point2D " +(i+1) + ": " + "( "
+ arrayPuntos[i].x + " , "
+ arrayPuntos[i].y + " )");
}
}
public static void printClosest(Points2DN puntos) {
Point p = puntos.points[puntos.closestPoints[0]];
Point q = puntos.points[puntos.closestPoints[1]];
System.out.println("\nThe closest points are: ");
System.out.println("Points: "
+ "(" + p.x + "," + p.y + ")" + " & "
+ "(" + q.x + "," + q.y + ")");
System.out.println("Distance: " + puntos.distance);
}
private void distances(Points2DN puntos) {
for (int i = 0; i < puntos.points.length; i++) {
// Iterative loop for the other points to be check with
for (int j = (i+1); j < this.points.length; j++) {
if (i == 0 && j == 1) {
int p = puntos.closestPoints[0] = i;
int q = puntos.closestPoints[1] = j;
puntos.distance = new BigDecimal((puntos.points[p]).distance(puntos.points[q])).setScale(3, RoundingMode.FLOOR);
continue;
}
BigDecimal distancePair = new BigDecimal(puntos.points[i].distance(puntos.points[j]));
if (distancePair.doubleValue() < puntos.distance.doubleValue()){
puntos.closestPoints[0] = i;
puntos.closestPoints[1] = j;
puntos.distance = distancePair.setScale(3, RoundingMode.FLOOR);
}
}
}
}
private void distances(Points2DN puntos, int x) {
for (int i = 0; i < puntos.points.length; i++) {
// Iterative loop for the other points to be check with
for (int j = (i+1); j < this.points.length; j++) {
if (i == 0 && j == 1) {
int p = puntos.closestPoints[0] = i;
int q = puntos.closestPoints[1] = j;
puntos.distance = new BigDecimal((puntos.points[p]).distance(puntos.points[q])).setScale(x, RoundingMode.FLOOR);
continue;
}
BigDecimal distancePair = new BigDecimal(puntos.points[i].distance(puntos.points[j]));
if (distancePair.doubleValue() < puntos.distance.doubleValue()){
puntos.closestPoints[0] = i;
puntos.closestPoints[1] = j;
puntos.distance = distancePair.setScale(x, RoundingMode.FLOOR);
}
}
}
}
/* main (String n, string x) {}
* Generates 'n' random 2D points
* Calculates which pair is the closest one
* Print the result including the distance with 'x' decimals
*/
public static void main(String[] args) {
try {
int numberOfPoints = Integer.parseInt(args[0]);
if (args.length == 1) {
Points2DN puntos = new Points2DN(numberOfPoints);
imprimePuntos(puntos.points);
printClosest(puntos);
}
if (args.length == 2) {
int x = Integer.parseInt(args[1]);
Points2DN puntos = new Points2DN(numberOfPoints, x);
imprimePuntos(puntos.points);
printClosest(puntos);
}
} catch (Exception ex) {
System.out.println(ex.toString());
}
}
}