Java ArrayList out of bounds exception

[grahamb314]

Hi there,
I have some code that does various simple things to some ArrayLists that I have created.

However, I get an out of bounds exception on the line i hightlight below
I have spent what must be an hour trying to solve what must be a simple problem!

For reference: distances is a 2Darray of type string with size of intSize(Currently 12) (A print of for it is below)

/**
 *
 * @author grahambthreeonefouratgmaildotcom
 * @version 1.0
 * Traveling Salesman Java Project
 * Start: 03/Nov/08
 * 
 */
//ERROR: Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 11, Size: 11

ArrayList cities = new ArrayList<Integer>();
System.out.println();
int d=1;
//Populate the arrayList with all cities) eg 1-12 where intSize=12
for(int i=0; i<intSize; i++) {
    cities.add(d);
    d++;
    //print Arraylist to test
    //System.out.println(cities.get(d-2)+ " ");
   }
System.out.println();
System.out.println();

 
while (cities.size() != 0) { //while not null (ATM it will always be null till finished)
   int x=0;
   Integer currentCity = ( Integer ) cities.get(x);
   cities.remove(x);
   
   int i=0;
   ArrayList tempCities = new ArrayList<Integer>();
   //get distances from this city to the rest into the Temp array list
   for (i=0; i<distances.length;i++)
   {
       int u =  distances[currentCity-1][i];
       //int u =  distances[5-1][i];
       tempCities.add(i,u);
       //print for testing
       //System.out.println(tempCities.get(i)+ " ");
   }
   System.out.println();
   
   
   
   
   
   //find smallest city in the temp array
   i = 0;
   int smallest = 999999999;
   for (i = 0; i<tempCities.size(); i++  ) {
       if (( Integer ) cities.get(i) == 0) {   //ERROR IS ON THIS LINE
           i++;
       }
       Integer curr = ( Integer ) cities.get(i);
      
       
    if ( curr < smallest) {  
        smallest = curr;
        System.out.println(smallest + " ");
    }
   }

distances array print out (not an arraylist)
0 53 6 8 20 40 15 7 30 29 2 3
53 0 30 35 50 5 6 10 12 20 30 32
6 30 0 4 10 15 15 9 9 9 8 3
8 35 4 0 7 21 14 13 12 11 17 8
20 50 10 7 0 30 32 34 20 6 40 25
40 5 15 21 30 0 9 14 7 13 31 32
15 6 15 14 32 9 0 4 21 25 15 16
7 10 9 13 34 14 4 0 31 35 4 10
30 12 9 12 20 7 21 31 0 5 50 40
29 20 9 11 6 13 25 35 5 0 27 21
2 30 8 17 40 31 15 4 50 27 0 5
3 32 3 8 25 32 16 10 40 21 5 0


Thanks!

[CJSLMAN]

In your for loop, you are incrementing variable "i" twice... once in the for statement and another in the for body:

for (i = 0; i<tempCities.size(); i++  ) {
       if (( Integer ) cities.get(i) == 0) {   //ERROR IS ON THIS LINE
           i++;//[COLOR="Red"]<-Is this supposed to be here? ALready have i++ above in for statement[/COLOR]
       }

Luck,
CJSL

[grahamb314]

In your for loop, you are incrementing variable "i" twice... once in the for statement and another in the for body:

for (i = 0; i<tempCities.size(); i++  ) {
       if (( Integer ) cities.get(i) == 0) {   //ERROR IS ON THIS LINE
           i++;//[COLOR="Red"]<-Is this supposed to be here? ALready have i++ above in for statement[/COLOR]
       }

Luck,
CJSL

Yea, the idea is if the element i am currently looking at = 0 then try the next one

I took it out and get the same error:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 11, Size: 11

[DarrylBurke]

> the idea is if the element i am currently looking at = 0 then try the next one
And what happens if the last element == 0? and there isn't a next one to try?

db

[grahamb314]

ah, okay that makes sence, but like i said, i have removed this from my code and I still get the same error .
Its definatly something to do with the way i have the for and if loops. I have moved them around etc, but no solution.
Any more thoughts?

i = 0;
   int smallest = 999999999;
   for (i = 0; i<tempCities.size(); i++  ) {
       if (( Integer ) cities.get(i) == 0) {
             System.out.println("There is a 0");
             //i++;
       }
       else{
           Integer curr = ( Integer ) cities.get(i);
           
           if ( curr < smallest) {  
             smallest = curr;
             System.out.println(smallest + " ");
      }    
    }
   }

[DarrylBurke]

Impossible to say with the snippet you posted. For example, we can't see where you initialize distances. At a quick check, it appears that tempCities.size() == distances.length. cities on the other hand is reducing in size() each time you remove() a city.

To get better help sooner, post a SSCCE : Java Glossary that clearly demonstrates your problem.

db