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Make a registry/database list in Java

I wonder how to make a registry/database list in Java. I mean if I, for example, have a variable called "data", and then I add a new entry to that called "name" with the value "David". Then I would call something like "data.name" to get the value "David".
As seen on this picture
I've been Googling but not finding anything about it.

It sounds like you want a Map from String to String. You can use a HashMap<String,String> for that.
// Create Map using HashMap
Map<String, String> data = new HashMap<String, String>();
// Set name
data.put("name", "David");
// Get name
String name = data.get("name");
System.out.println(name);

Using something other than an ArrayList

I have a problem which requires me to create an array that will store the name of a file, and then its contents. I tried to use this, to create an Array ArrayList<String, String> fileContent = new ArrayList<String, String>(); but it calls an error, that there are an incorrect number of arguments. Whats the best way to get around this problem?
Would it be better to make two Arrays, one that stores the names, and one that stores the data in the file. Or is there another inbuilt thing inside of java that would be better to use?

create a custom class
class MyClass{
String filename;
String content;
}
// use methods as you want
then use array list for MyClass
ArrayList<MyClass> fileContent = new ArrayList<MyClass>();

If you are going to increase the properties you want to store, the answer by #while true is the correct one. If you want to store the name and the file only, you can create a HashMap like this.
HashMap<String, File> myMap = new HashMap<String, File>();
And insert elements like this:
myMap.put("filename",myFile);
Hope it helps.

Create a class that stores what you want, like this:
class Contents {
String fileName;
ArrayList<String> fileContent;
public Contents(String fileName){
this.fileName = fileName;
fileContent = new ArrayList<String>;
}
//Any Methods you need
}
and create an ArrayList like this:
ArrayList<Contents> = new ArrayList<Contents>;
This way you can store the fileName and it's contents.
The error you get is because an ArrayList can only contain one class, like String or in this example Contents.

Getting the user to name the variables

For my program i want to have it so that the user can name the variables a bit like in a game you would name your charecter/world. I looked it up and couldn't find anywhere that said if this is possible and if so how it is done.

As many others have said, you can't dynamically name variables.
You can however make a Map
It would allow you to create any name for a variable such as "MyTestVar" at runtime and use it as a key in that map to whatever you put:
Map<String, String> myMap = new HashMap<String, String>();
String varName = getVariableNameFromUser();
String value = getValueFromUser();
myMap.put(varName, value);
// ... later
String whatVariableDoYouWantTheValueOf = getVarNameFromUser();
String storedValue = myMap.get(whatVariableDoYouWantTheValueOf);
System.out.println("The value for that is: " + storedValue);

What you can do is create a linked list or an arraylist of some type of object that you create. Your object can then have two properties (or more) where one is the name, and the other is the value. You can then search for an object in your list based on the name, and return the value that you want. This will basically accomplish what you're trying to achieve.

You can't get a user to name a variable. All you can do is allow the user to set the variable's value.

I guess what you mean is something like giving Tags or Labels to Objects. "Variable Names" is a missleading wording for that.
After the User typed in the name string for an obj Object, you could for example use a HashMap<String, Object> to store the user input:
Map<String, Object> tagToObjectStore = new HashMap<String, Object>();
String userInput = "any Tag name";
Object somethingToLabel = ... // TODO
tagToObjectStore.put(userInput, somethingToLabel); // store the user input
// later in code...
Object theStoredObject = tagToObjectStore.get(userInput); // get the stored object
Is that what you are looking for?

HashMap<String, Object> : How to put Object itself as in place of String

A a = new A(); //classA { }
HashMap<String, Object> hm = new Hashmap<String,Object>();
hm.put("A", a);
My question is, How can i put the Object itself instead of "A" in same declaration?
hm.put(`a??`, a);

You simply cannot do that, the language prohibits it. It would only be possible if your class A is a subclass of String which is not possible, since String is declared as final in Java.
With respect to you interview question: It's not possible due to the generic type parameter that was chosen for the declaration. You can read more about that in Bounded Type Parameters.

A a = new A(); //classA { }
Map<A, A> hm = new Hashmap<A, A>();
hm.put(a, a);
But I do not see any point of putting a->a

If the class held a non-changing decent String field, you could use that.
// the id property must be a String, immutable and unique for each instance!
myMap.put(a.getId(), a);

If you want to make any object as a key in your HashMap, then that object has to be immutable.. Because, you don't want anyone to change your key, after you add them to your HashMap..
Just imagine, if your keys are changed after insertion, you won't ever be able to find your inserted value..
But if your key is immutable, then if anyone tries to change your keys, he will actually create a new one for himself, but you will still have yours..
That is what happens in case you use String as your key in HashMap(They can't be changed).. So, if you want your object to be a key, either you make your class a subclass of String (that you can't do), or, just make your class immutable..

This is actually possible using a raw type, like this:
Object key = ...;
Object value = ...;
Map<String, Integer> map = new HashMap<>();//a normal map
Map rawMap = map; // here is the raw type
rawMap.put(key, value); // it works!
This runs fine, but problems arise when you try to use the generic map later:
Integer value = map.get(key);// ClassCastException (unless value actually is an Integer)
That's why you were told that it's a "dirty trick". You shouldn't use it.

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

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

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)

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.

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.