Java coding style - passing array of String to multiple methods again and again

Question

Is this good coding in java?:

I have an String array. String[] strArr = .... Now I want to process on it and get the result, so I made a method taking a String array as an argument like,

public bopolen processArray(String[] srtArr){
   // .... some processing
   // loop over string array, process it and create a 
   // list of objects with same size as array
   List<Object> objList = new ArrayList<Object>(strArr.length);
   for(String str : strArr) {
       String[] anotherStrArr = str.split(",");
       Object myObj = new MyObject(anotherStrArr[0],anotherStrArr[1]);
       objList.add(myObj);
   }
   // .... some more processing
   // ....
   // loop over list and call another method 
   // that also takes an String array as argument like
   for (Object obj: objList) { <-- will loop same times as for the String array.
      boolean res = processData(obj.getDataMethod(), strArr); <-- again pass the same array as argument to another method. 
      // This method will get called as many time as array length.
   }
}

Now the second method:

public boolean processData(String data, String[] strArr) {
   // ..... some processing.
   // loop over String array and compare with data to process.
   for(String str: strArr) {
       String[] againStrArr = str.split(",");
       if(againStrArr[0].equals(data)) {
            // ... process on data and get the result.
       }
   }
   // ..... other statements of method.
}

So as you can see I'm passing same array to 2 methods and loop over it again and again. Is this good practice in java as my array size is very long, around 2000 elements in normal case.

---

Explanation on why I'm looping this much:

I got a String array from request which contains db_name and db_score of myObject which I have to update in database. Each element in strArr is comma separated db values like db_name,db_score. So first I loop over array and create a String of all names comma separated and then query in database to create List of MyObject. Then I loop over this list to update myObj with new score but to get exact score of name I again have to loop over array and compare name then get its score.

---

This is my table called Players:

id | name   | score
1  | mark   | 5
2  | mark_1 | 5
3  | mark_2 | 5
4  | mark_3 | 5

Sample data in string array: {"mark,10","mark_1,15","mark_2,20","mark_3,30"}

Now I iterate through array and create comma separated name string and use that in query like:

select * from myObject where name in ('mark','mark_2','mark_2','mark_3')
                                     |_________________________________|
                                                     |
                    this much part is built from looping over the String array

So first iteration is for creating where clause of query. Now this query returns List of MyObject. Second time I iterate through this list to update score of players. But to get score of particular player name I again have to iterate over strArray and find it. So for each element in list I have to call a method and pass playerName and strArr to get it's score and then finally update it in database.

Answer 1

Don't worry about it. When you pass the array, the array itself is not copied to the stack, just a reference to it. It's perfectly fine to pass the array to as many methods as you like; and the size of the array won't make any difference to the performance (except of course for within the methods themselves).

Answer 2

Instead of the objList You can use the array of 'MyObject' the length of this is equal to the length of the 'strArr' I guess you can use only method to process array and data and use only one for loop as the strArr is already available so the count of iteration is defined.

Answer 3

Per your final explanation, no you don't need to iterate twice, here are few ways you can solve your issue:

First solution
Instead of creating the WHERE clause for all items, why not just update directly with the name being the WHERE clause. For example

loop through all names and scores (your original array)
    split the name and score
    execute an update on database(param_player_name,param_player_score)

Update statement:

UPDATE Players  
SET score = param_player_score  
WHERE name = param_player_name;

Second solution (not recommended, but just for info)
Instead of looping again, just add your objects to a HashMap instead of an array. example:

Map<String,Long> myMap = new HashMap<String,Long>();
loop through all names and scores (your original array)
     myMap.put(name,score);

That way you made the name the key of the Map, and to retrieve the score (in second loop), you just call:

Long score = myMap.get(name);

As I said, the next solution is not recommended, since it will still need you to generate a very long WHERE clause which is not a good idea, and might cause problems if number of players increases too much.

IMPORTANT NOTE
When dealing with database, always use the ID of the column instead of anything else when updating and retrieving data. So, your WHERE should filter by your id column always, supposing it's Unique and NOT NULL whereas your Name field by not be Unique and might be NULL

Answer 4

Java runtime environment has a good memory management. It even cleans unused variables when not in used... so you can even declare an array with million elements.