index out of bounds exception java [duplicate]

Question

So the error message is this:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at FcfsScheduler.sortArrival(FcfsScheduler.java:77)
at FcfsScheduler.computeSchedule(FcfsScheduler.java:30)
at ScheduleDisks.main(ScheduleDisks.java:33)

with my code as

public void sortArrival(List<Request> r)
{
    int pointer = 0;
    int sProof = 0;
    while(true)
    {
        if(r.get(pointer).getArrivalTime()<r.get(pointer+1).getArrivalTime())
        {
            Request r1 = r.get(pointer);
            Request r2 = r.get(pointer+1);
            r.set(pointer, r2);
            r.set(pointer+1, r1);
        }
        else
        {
            sProof++;
        }
        ++pointer;
        if(pointer>r.size()-2)
        {
            pointer=0;
            sProof=0;
        }
        if(sProof>=r.size()-2)
        {
            break;
        }
    }
}

The error is at

if(r.get(pointer).getArrivalTime()<r.get(pointer+1).getArrivalTime())

but I think the array index is checked ok with the code after the increment of pointer. Is it an array out of bounds exception or something else? Normally, the error is ArrayIndexOutOfBoundsException when it is the array. What seems to be the problem here?

Try debugging your code using debugger, you can get exactly where and how error is occurring. — Pradeep Simha
– Pradeep Simha, Commented Mar 17, 2013 at 15:41
you should check pointer+1 against the size of r in your while decleration to avoid this error. also, checking that r is not null and not empty may be a good idea. — Oren
– Oren, Commented Mar 17, 2013 at 15:45
Possible duplicate of What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it? — jww
– jww, Commented Jun 12, 2019 at 15:47

Ajay S · Accepted Answer · 2013-03-17 15:54:51Z

6

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

ArrayList is empty. It does not contain any element.

Index: 0, Size: 0.

You are trying to access it.So you are getting IndexOutOfBoundsException.

if(r.size() == 0) && r.size() < pointer + 1)   //If ArrayList size is zero then simply return from method.
  return;

edited Mar 17, 2013 at 15:54

answered Mar 17, 2013 at 15:42

Ajay S

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Raunak Agarwal · Accepted Answer · 2013-03-17 15:44:58Z

5

You are passing in an empty array. You should do some validation on the inputs

if (r == null || r.size()==0){
   throw new RuntimeException("Invalid ArrayList");
}

answered Mar 17, 2013 at 15:44

Raunak Agarwal

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Comments

mkazma · Accepted Answer · 2013-03-17 16:42:19Z

0

Your array size is 0, you should initialize it correctly in order to iterate it.

answered Mar 17, 2013 at 16:42

mkazma

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