Question

Hi all I’m using a HashMap to hold one of my object with a string key. when I put an object with a key it has no problem, when I put my second object I got my object added but can’t get it with its key. Somewhat it goes to somewhere that is “next”. I took a screenshot from debug mode (eclipse), below

although size shows 2, I can’t see my second item in hashmap, but in other hashmap’s next node.

To note something I use my key like in a form “name.tag”, tag and name in same time can never be the same, but “tag” can be the same. does hashmap has something to do with dot operator when evaluating keys? I hope I could write clearly,

Thanks in advance

Edit:
Here is a piece of code I use to create my hashmap

        private HashMap<String,ParameterItem> parseParametersNode(DataModel parent,Element element){
        NodeList parameterChilds=element.getChildNodes();//gep element parameters
        HashMap<String, ParameterItem> parameterItems=new HashMap<String, ParameterItem>();
        for(int i=0;i<parameterChilds.getLength();i++){
            if(parameterChilds.item(i).getNodeType()==Node.ELEMENT_NODE){
                Element el=(Element) parameterChilds.item(i);
                NamedNodeMap atts=el.getAttributes();
                ParameterItem item=new ParameterItem();

                for(int j=0;j<atts.getLength();j++){
                    Attr attribute=(Attr) atts.item(j);
                    String attributeValue=attribute.getValue();
                    String attributeName=attribute.getName();
                    item.setParsedProperty(attributeName, attributeValue);
            } /*check  attributes later*/
                //finish loop and insert paramitem to params
                String key="key"+i;
                if(item.getTag()!=null && item.getName()!=null)
                    key=item.getName()+"."+item.getTag();
                parameterItems.put(key, item);
//              testParam=item;
//              parameterItems.put(key, testParam);
                }
        }
        return parameterItems;

    }

Answer 1

There is not really a problem here: you have a hash collision. That is, both of your keys have been placed in the same hash bucket. It appears you have only four buckets (odd, I thought the initial default was 10 or 16), so the chance of that with random data is 25 percent. Your size incremented just fine. The next is the internal implementation’s way of pointing to the next element in the same bucket. If the number of elements in each buckets gets too big, Java will internally rehash into more buckets.

I do not see why you need a HashTable here since you are numbering your keys consecutively (you could use an ArrayList), but maybe this is just starter code and your real use case is different.