Question

I have a problem on arraylist and hashmap

As according to my requirement, I am storing the data into HashMap and after that I have created a List as List>.

        HashMap<String,String> hashmap;
        static List<HashMap<String,String>> hashmap_string;

And while retrieving the value from database and putting it on HashMap and ArrayList like:

                    contract_number=c.getString(c1);
                    Log.i("c1.getString,contract_number", contract_number);
                    String service_level=c.getString(c2);
                    hashmap=new HashMap<String, String>();
                    hashmap.put(contract_number, service_level);
                    hashmap_string.add(hashmap);

And now I want to retrieve the value as String,String

And when I am applying the code as:

                for(int i=0;i<hashmap_string.size();i++)
                {
                    Log.i("arraylist", ""+hashmap_string.get(i));
                }

I am getting a single string value in the formet as

               {Contract,ServiveValue}

but I want to split this into 2 string values…Also these values are redundant and if am using hashMap then it will not showing me the redundant value.

Please help me on this..

Answer 1

HashMap (and Maps in general) are used for multiple one-to-one mappings of keys and values. Are you sure you need that? Looking at your code it appears you’re using the map as a “Pair” class. I would skip the list, and put everything in the same map, and then iterate over the pairs in the map:

// using tree map to have entries sorted on the key, 
// rather than the key's hash value.
Map<String, String> data = new TreeMap<String, String>();
data.put("c1", "s1");
data.put("c2", "s2");

for (Map.Entry<String, String> entry : data.entrySet()) {
    String contract = entry.getKey();
    String level = entry.getValue();
    Log.i("data", contract + " : " + level");
}

would output (assuming TreeSet):

c1 : s1
c2 : s2

Alternatively, create e.g. a ContractServiceLevel class that holds two strings (the contract number and the service level), and put instances of that class in your list.

EDIT:

public final class ContractServiceLevel {
    public final String number;
    public final String serviceLevel;

    public ContractServiceLevel(String c, String s) {
        number = c;
        serviceLevel = s;
    }
}

List<ContractServiceLevel> contracts = new ArrayList<ContractServiceLevel>();
contracts.add(new ContractServiceLevel("c1", "s1.1"));
contracts.add(new ContractServiceLevel("c1", "s1.2"));
contracts.add(new ContractServiceLevel("c2", "s2.1"));

for (ContractServiceLevel contract : contracts) {
    Log.i("data", contract.number + ":" + contract.servicveLevel);
}

would output:

c1 : s1.1
c1 : s1.2
c2 : s2.1