java.lang.ArrayIndexOutOfBoundsException: 48

Question

I have an exercise on Dijkstra's Algorithm and when I run my programm I get the following error: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 48
What is wrong? I can't sent the entire code because it is 200 lines. But the problem appears in those lines in cmd
dist[i] = Integer.MAX_VALUE; and dist[i] = 0;

Thanks in advnace for your help.

public static void DijkstraOnNode (int start) {

  int[] dist = new int [myNodes.size()]; //where myNodes is an ArrayList of Hashset<Link>
                                         //and Link is a class that contains node kai weight       
  int[] pred = new int [myNodes.size()];  
  int[] pq = new int [myNodes.size()];

 for (int i = 0; i <= myNodes.size(); i++) {

    if (i!= start)
        dist[i] = Integer.MAX_VALUE;
    else
        dist[i] = 0;

   pq[i] = dist[i];
}

(the code continues)

Arrays are 0 base indexed. So it should be `for(int i = 0; i < myNodes.size(); i++) {` — Alexis C., Apr 14 '14 at 16:38
Possible duplicate of [What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it?](http://stackoverflow.com/questions/5554734/what-causes-a-java-lang-arrayindexoutofboundsexception-and-how-do-i-prevent-it) — Alex Celeste, Oct 18 '15 at 16:25

score 3 · Accepted Answer · answered Apr 14 '14 at 16:38

3

for (int i = 0; i <= myNodes.size(); i++)

This causes the problem change it to

for (int i = 0; i < myNodes.size(); i++)

Because, lets say myNodes.size() returns 8 and you are trying to reach dist[8] but dist[] array starts at 0 and ends at 7.

answered Apr 14 '14 at 16:38

Salih Erikci

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Better yet use `dist.length` – Ingo Apr 14 '14 at 16:42
I did so, but when I run the programm again in cmd it returns nothnig. Either it will let me type anything. Like a non stop loop. But perhaps thats a problem in another method.. Thanks anyways! – MariaP Apr 14 '14 at 16:46
@MariaP your method is void and doesn't print out anything. – Salih Erikci Apr 14 '14 at 16:49
Well i have in the method if (printArrays) { System.out.println("Predecessor matrix"); System.out.println(Arrays.toString(pred)); and when i want to run just the algorithm printArrays is initialized as false but when I want to print them I initialize it with true. Does void not allow it? – MariaP Apr 14 '14 at 17:01
@MariaP it is ok then. You can print in a void method. – Salih Erikci Apr 14 '14 at 19:32

score 0 · Answer 2 · answered Apr 14 '14 at 16:50

Arrays: numbering begins with 0. The 9th element, for example, would therefore be accessed at index 8. So in the loop:

for (int i = 0; i <= myNodes.size(); i++)

you try to access the element of the array : dist[myNodes.size()] which does not exist. It's Out Of Bounds of the array. The last element of the array has index: myNodes.size() - 1

You could see more about arrays here: http://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html

java.lang.ArrayIndexOutOfBoundsException: 48

2 Answers2