java.lang.OutOfMemoryError: Java heap space on using ArrayLists

Question

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf(Unknown Source)
    at java.util.Arrays.copyOf(Unknown Source)
    at java.util.ArrayList.grow(Unknown Source)
    at java.util.ArrayList.ensureExplicitCapacity(Unknown Source)
    at java.util.ArrayList.ensureCapacityInternal(Unknown Source)
    at java.util.ArrayList.add(Unknown Source)
    at FibonacciHeap.removemax(FibonacciHeap.java:148)
    at UseFibonacciHeap.main(UseFibonacciHeap.java:61)

My java program on Eclipse is reading strings from a file and inserting them to an array list and doing a lot of computations ahead.It throws the above exceptions on encountering 150+ strings.I tried increasing the VM space,using sleep but Nothing works ! The eventual goal is to operate on 1 million strings(not all unique).

Edits:

Usage of the ArrayList toVisit:

for (FibonacciNode curr = max_ptr; toVisit.isEmpty() || toVisit.get(0) != curr; curr = curr.right_sibling)
{
     toVisit.add(curr);
     ...
}

VM Arguments for the class: -Xms1024M -Xmx1524M

Can someone guide me to an optimal way of doing this.Is there a different data structure that I can use? Thanks !!

add your code to the question. Arraylist shouldn't run out of memory this quickly, so its very likely that the error is in how you are using your arraylist — baseballlover723
– baseballlover723, Commented Nov 12, 2016 at 6:20
can you give some more context to the code? what are all of the variables? where do they come from? I would guess that you have an infinite loop somewhere. — baseballlover723
– baseballlover723, Commented Nov 12, 2016 at 6:31
Most likely your for loop is looping forever. Check the 'while' part of the loop (toVisit.isEmpty() || toVisit.get(0) != curr) - does this ever become false? — greg-449
– greg-449, Commented Nov 12, 2016 at 8:15
Do your algorithm do exactly what you expect? Use print statements and a debugger to learn what happens. If it does what you expect, then why does it need so much memory? — Thorbjørn Ravn Andersen
– Thorbjørn Ravn Andersen, Commented Nov 12, 2016 at 11:33

iBiber · Accepted Answer · 2016-11-12 06:46:31Z

1

I think the problem Is located in your algorithm and not in your memory setting.

First you should check what the code does at the lines which are printed in the stacktrace: at FibonacciHeap.removemax(FibonacciHeap.java:148) at UseFibonacciHeap.main(UseFibonacciHeap.java:61)

answered Nov 12, 2016 at 6:46

iBiber

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Steve Johnson · Accepted Answer · 2016-11-12 06:27:38Z

0

You can increase your heap space with -Xmx6g, but 150 strings seems like an awfully small number to blow heap up. Make sure you're using StringBuffer or StringBuilder instead of String.

answered Nov 12, 2016 at 6:27

Steve Johnson

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