[英]Java Array Index out of Bounds Error
我正在研究旅行商问题的蛮力方法。 我有一行会产生ArrayIndexOutOfBounds
异常,但是那里使用的所有数组都有足够的空间。 特定的代码行:
testCity[0][a] = cities[0][(int) cityList[a]];
这是我初始化testCity
:
int[][] testCity = new int[2][CITIES+10];
cities
:
public static int[][] cities = new int[2][CITIES+10];
最后, cityList
:
Object[] cityList = new Integer[CITIES+10];
这是整个错误消息:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
at BruteF.permute(BruteF.java:39)
at BruteF.permute(BruteF.java:30)
at BruteF.permute(BruteF.java:30)
at BruteF.permute(BruteF.java:30)
at BruteF.main(BruteF.java:11)
这是代码:
public class BruteF {
public static final int CITIES = 5;
public static int[][] cities = new int[2][CITIES+10];
public static int[][] bestCity = new int[2][CITIES+10];
public static double bestDistance = 1000;
public static int[][] testCity = new int[2][CITIES+10];
public static Object[] cityList = new Integer[CITIES+10];
public static void main(String[] args)
{
permute(java.util.Arrays.asList(1,2,3,4), 0);
for (int i = 0;i < CITIES;i++)
{
System.out.println(bestCity[0][i] + "," + bestCity[1][i]);
}
}
static void permute(java.util.List<Integer> arr, int k){
cities[0][0] = 1;
cities[1][0] = 1;
cities[0][1] = 2;
cities[1][1] = 5;
cities[0][2] = 3;
cities[1][2] = 2;
cities[0][3] = 4;
cities[1][3] = 3;
int originalX = cities[0][0];
int originalY = cities[1][0];
for(int i = k; i < arr.size(); i++){
java.util.Collections.swap(arr, i, k);
permute(arr, k+1);
java.util.Collections.swap(arr, k, i);
}
if (k == arr.size() -1){
for (int i = 0;i < CITIES;i++)
{
cityList = arr.toArray();
for (int a = 0;a < CITIES;a++)
{
testCity[0][a] = cities[0][(int) cityList[a]];
}
if (distance(testCity,CITIES,originalX, originalY) < bestDistance)
{
bestCity = testCity;
bestDistance = distance(testCity,CITIES, originalX, originalY);
}
}
}
}
static double distance (int[][] cities, int CITIES, int originalX, int originalY)
{
int[][] taken = new int[2][CITIES+1];
int takenCounter = 0;
double distance = 0;
cities[0][CITIES] = cities[0][0];
cities[1][CITIES] = cities[1][0];
for (int i = 0;i <= CITIES;i++)
{
for (int z = 0;z <= CITIES;z++)
{
if (cities[0][i] == taken[0][z] && cities[1][i] == taken[1][z])
{
return CITIES*1000; //possible error here
}
else {
taken[0][takenCounter] = cities[0][i];
taken[1][takenCounter] = cities[1][i];
}
}
if (cities[0][0] != originalX && cities[1][0] != originalY)
{
return CITIES*1000; //POSSIBLE BUG HERE
}
distance = distance + Math.sqrt(Math.pow(cities[0][i+1]-cities[0][i],2) + Math.pow(cities[1][i+1]-cities[1][i],2));
}
return distance;
}
}
为什么会发生这种情况? 我能做些什么来修复它?
它给出了越界异常:4
当你初始化 cityList ie cityList = arr.toArray(); 您的数组 cityList[] = {1,2,3,4} ,即从 0 到 3 的大小为 4。
你正在运行一个 for 循环,即
for (int a = 0;a < CITIES;a++)
从 a=0 到 CITIES ,所以当 a=4 时刻到来时,它会给出越界错误。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.