OutOfMemoryError: Java heap space while converting some bulk data to toString()

Question

I am facing java.lang.OutOfMemoryError: Java heap space. Some bulk amount of data converting into toString(). I have my own implementation of toString code. You can see below code:

String dataStr = (new LargeData(objData)).toString();

public String toString() 
{ 
    try 
    { 
       if (localBase64Binary != null) 
       { 
           ByteArrayOutputStream out = new ByteArrayOutputStream(); 
           localBase64Binary.writeTo(out); return out.toString("utf-8"); 
       } 
     } 
    catch (IOException ex) 
    { 
       ex.printStackTrace(); 
    } 
    return null; 
}

I am using maximum heap space -Xms128m -Xmx256m. If I increase heap space just I can postpone out of memory some days only. Is there any way to optimize the code in this situation?

Can any one please guide me or help me to resolve this issue?

Please check my toString code below public String toString() { try { if (localBase64Binary != null) { ByteArrayOutputStream out = new ByteArrayOutputStream(); localBase64Binary.writeTo(out); return out.toString("utf-8"); } } catch (IOException ex) { ex.printStackTrace(); } return null; } — user1575538
– user1575538, Commented Aug 4, 2012 at 3:43
@user Please post the code in question only and use {} tags present in the editor window to format the code. — Mahesh
– Mahesh, Commented Aug 4, 2012 at 3:49

dsh · Accepted Answer · 2012-08-04 03:55:01Z

3

One problem is dynamically resizing arrays to add more elements. This requires allocating a new array larger than the existing array and then copying the elements. If the new array is larger than half the heap space it is guaranteed to fail.

The solution to your problem is to not use .toString(). Instead of trying to keep all the data in RAM, pass a file stream to the method and write the data to disk (or stream it to a socket, or a pipe).

answered Aug 4, 2012 at 3:55

dsh

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Comments

Peter Lawrey · Accepted Answer · 2012-08-04 08:05:22Z

1

In stead generating a large string and passing to something else to do something with, you need to process the data produced as you generate it.

e.g. instead of

String dataStr = (new LargeData(objData)).toString();
out.println(dataStr);

do

new LargeData(objData).writeTo(out);

as this will use much less memory at once.

answered Aug 4, 2012 at 8:05

Peter Lawrey

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