Using one variable as an another variable of different data type but the same name

Question

I am using a class where I am taking input as the file name and the file location. I have a pre defined file names, so I will match the predefined file names with the file name that I received and then store the values accordingly. Please look at the code below

//Set of storage maps and tables 
public class storage
{
//Storage set
public static Set<Integer> tiger = new HashSet<Integer>();

//Storage set
public static Set<Integer> lion = new HashSet<Integer>();

//This is the table used for storing the browser customer count  
public static Table<String,String,Integer> elephant = HashBasedTable.create(); 

//Storage map 
public static Map<String, String> monkey = new HashMap<String, String>();


public static void storeDataDirector(String fileLocation,String fileName) throws     Exception 
{
    if (fileName = monkey) 
                **update the "monkey map"**

}

This is my problem, also I have lot of maps and tables to be used so I wouldn't be able to use multiple if conditions and then check and update the same.

What I would like to know is the below

As I have said earlier, The file name that I am sending to the program which is "String filename" has the same name of the "Map monkey" but the former is a String and the latter is the map. I would like to know if I will be able to use the string variable as a reference to the map instance as both of them have the same name . This will highly avoid the if conditions that I am using in the program and thus I would like to possible solution for this ... Anything related to type caseting ort

First of all, = is no a comparison, but an assignment. Second: Use "monkey".equals(fileName) for String comparison. — Baz
– Baz, Commented Jul 28, 2012 at 19:19

Bhaskar · Accepted Answer · 2012-07-28 19:29:27Z

2

You need to have another Map - whose key is a String and value is a Map. Something like Map<String,Map> allMaps = new HashMap<String,Map>()

Once you have this map , populate it with all your filenames and the corresponding maps monkey.

allMaps .put("monkey", monkey)

If a string filename corresponds to not a map but to a set , then you need to declare something more general Map<String,Object> allMaps = new HashMap<String,Object>(). Ofcourse this means you need to cast the value to its particular type before you can do any meaningful thing with it.

Then , to use this map , use your filename argument

Map monkeyAgain = allMaps.get(filename)

answered Jul 28, 2012 at 19:29

Bhaskar

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Comments

Benoit · Accepted Answer · 2012-07-28 19:29:49Z

1

You can use reflection:

Storage.class.getField(fileName).get(null)

You will still have to cast the returned object. I do not think this the right approach.

answered Jul 28, 2012 at 19:29

Benoit

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1 Comment

Louis Wasserman Over a year ago

+1 for "this is not the right approach." The OP really ought to rethink the design here.

Francisco Spaeth · Accepted Answer · 2012-07-28 19:38:32Z

The idea is to relate them in a Map, and use the file name as a key for example

Map<String, Map<String, String>>
//  file    store structure

If you need a generic solution, you could solve this by implementing an abstraction of your store structure, by implementing an interface similar to this one:

// T is the store type and U is the original type (String from file for instance...)
public interface StoreUnit<T, U> {

    void update(U record);

    List<T> list();

}

so you will have an implementation for each case (Set, Map, Table ...) and will relate it in a map using the file name as key.

monkeyFileName => MapStoreUnit<Entry<String,String>,String>
tigerFileName => SetStoreUnit<Integer, String>
elephantFileName => TableStoreUnit<Entry<Entry<String,String>,String>,String> // not sure if for Table there is something better than Entry ;)

When you wanna update some store you perform a get over the map using the file name as key, and invoking update method implemented with the record (that could be an String, complex Object) and so on. When you need to read something from there you could use the list method.

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