StackOverflowError using hashCode() in HashMap in recursive method

[Edward Martinez]

Hi everyone,
OK, I'm really stumped here. I'm getting a StackOverflowError, which is occurring on the first line of my overridden hashCode() method of my POJO. hashCode() is being called from the get() method of HashMap, which is used in a recursive method. The map is not self-referential. Here's a snippet of hashCode().

	public int hashCode() {
		final int PRIME = 31;
		int result = 1;
		result = PRIME * result + ((gneIp == null) ? 0 : gneIp.hashCode());
		result = PRIME * result + ((gneTid == null) ? 0 : gneTid.hashCode());
		result = PRIME * result + ((market == null) ? 0 : market.hashCode());
		result = PRIME * result + ((objectId == null) ? 0 : objectId.hashCode());
		result = PRIME * result + ((tid == null) ? 0 : tid.hashCode());
		result = PRIME * result + ((tidAlias == null) ? 0 : tidAlias.hashCode());
		result = PRIME * result + ((type == null) ? 0 : type.hashCode());
		result = PRIME * result + ((fni == null)  ? 0 : fni.hashCode());

		return result;
	}

This is generated by Eclipse.

Here's what the recursion looks like:

	public void buildWorkingSegments(NsmTid tid, NsmTid zTid, Map<String, NsmSegment> segmentMap, 
	                                 List<NsmSegment> workingSegments, int nodeCount, NsmFni fni)
	                                    throws MalformedRingException
	{
	            
	    log.debug("buildWorkingSegments() - start");
	    
	    NsmSegment segment = segmentMap.get(tid.getTid());
	            
	    workingSegments.add(segment);
	    
	    NsmTid segmentZTid = null;
	    
	    try
	    {
	        segmentZTid = segment.getNsmPortByZendport1aid().getNsmCard().getNsmTid();
	    }
	    catch (RuntimeException e)
	    {
	        log.error("Error building UPSR ring: " + fni.getFni());
	        log.error("segment " + (segment != null ? segment.getSegmentname() : "(Segment not available) ") + " has no Z tid.");
	        
	        throw new MalformedRingException(e);
	    }
	    
	    if (segmentZTid.equals(zTid))
	    {
	        log.debug("buildWorkingSegments() - terminating.");
	        
	        return;
	    }
	    
	    if (nodeCount == segmentMap.size() - 1)
	    {
	        log.error("Error building UPSR ring: " + fni.getFni());
	        log.error("Z tid " + zTid.getTid() + " never reached.");
	        
	        throw new MalformedRingException("Z tid " + zTid.getTid() + " never reached.");
	    }
	    
            nodeCount++;
	    
	    buildWorkingSegments(segment.getNsmPortByZendport1aid().getNsmCard().getNsmTid(), zTid, segmentMap, workingSegments, nodeCount, fni);
	}

Any ideas anyone has would be greatly appreciated.

Thanks,

Eddie

[Piet Verdriet]

Well, apparently

if (segmentZTid.equals(zTid))

never happens and you keep recursively calling the method. Have you overridden the equals(Object) method as well? Can you post it here?

[Edward Martinez]

Hi Piet,
Thanks for your response. Sorry it took me so long to get back to you.

Here are the attributes of my class:

    

	private String tid;

	private Long objectId;

	private String type;

	private String market;

	private Date loadDate;

	private String gneTid;

	private String gneIp;

	private String tidAlias;

	private String fni;	

Here's my equals() method, which was generated by Eclipse:

  

	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		final NsmTid other = (NsmTid) obj;
		if (gneIp == null) {
			if (other.gneIp != null)
				return false;
		} else if (!gneIp.equals(other.gneIp))
			return false;
		if (gneTid == null) {
			if (other.gneTid != null)
				return false;
		} else if (!gneTid.equals(other.gneTid))
			return false;
		if (market == null) {
			if (other.market != null)
				return false;
		} else if (!market.equals(other.market))
			return false;
		if (objectId == null) {
			if (other.objectId != null)
				return false;
		} else if (!objectId.equals(other.objectId))
			return false;
		if (tid == null) {
			if (other.tid != null)
				return false;
		} else if (!tid.equals(other.tid))
			return false;
		if (tidAlias == null) {
			if (other.tidAlias != null)
				return false;
		} else if (!tidAlias.equals(other.tidAlias))
			return false;
		if (type == null) {
			if (other.type != null)
				return false;
		} else if (!type.equals(other.type))
			return false;
		if (fni == null) {
			if (other.fni != null)
				return false;
		} else if (!fni.equals(other.fni))
			return false;		

		return true;

I may have found a workaround for this. I started using a String as the key in the HashMap, rather than the complex type, and the infinite recursion has disappeared, so far. I'm going to let it soak for the rest of this week and see how it does.

Thanks for your help,

Eddie

[Rob Spoor]

That equals method looks really ugly. With just a little utility method you can make it so much easier to read:

private static boolean equals(Object o1, Object o2)
{
     return (o1 == null ? o2 == null : o1.equals(o2));
}

public boolean equals(Object obj)
{   
    if (this == obj)   
        return true;   

    if (obj == null || getClass() != obj.getClass())   // combined
        return false;   

    final NsmTid other = (NsmTid) obj;   
    return equals(gneIp, other.gneIp) &&
           equals(gneTid, other.gneTid) &&
           equals(market, other.market) &&
           equals(objectId, other.objectId) &&
           equals(tid, other.tid) &&
           equals(tidAlias, other.tidAlias) &&
           equals(type, other.type) &&
           equals(fni, other.fni);
}

[Piet Verdriet]

Rob Prime wrote:... With just a little utility method you can make it so much easier to read:
...

Indeed!

[Campbell Ritchie]

You should never actually look at an automatically generated method. Not unless you have a very strong stomach