I don't have the time to code this but I would use the picard API: Open a bam:

 SAMFileReader sf=new SAMFileReader(bamfile);
sf.setValidationStringency(SAMFileReader.ValidationStringency.LENIENT);

create an iterator scanning a region overlaping the SNP:

IntervalList iL=new IntervalList(sf.getFileHeader());
 iL.add(interval);
SamLocusIterator sli=new SamLocusIterator(sf,iL,true);

loop over the iterator. Get the reads overlapping the SNPs:

                    SamLocusIterator sli=new SamLocusIterator(sf,iL,true);          
                    sli.setMappingQualityScoreCutoff(this.minQual);
                    for(Iterator<SamLocusIterator.LocusInfo>  iter=sli.iterator();
                        iter.hasNext();
                        )
                        {
                        SamLocusIterator.LocusInfo locusInfo=iter.next();
                        int position=locusInfo.getPosition();
                        for(SamLocusIterator.RecordAndOffset aro: locusinfo.getRecordAndPositions())
                         { 
                         /* implement the logic here  ....  record the quality for each base/samRecord/position*/
                         }
                        }
                    sf.close();