CODEWITHSUNDEEP
javaarraysrecursion
Julia
Julia

Reputation: 1237

Recursively get strings from array columns

I have an array of objects. Content of each array element can be String, or it can again be another array with strings. Or it can be again array of arrays that hold strings.

Example: 

Object obj1 = array[[str1, str2, str3], [str4, str5]] 

or: Object obj2 =array [str1, str2]

or: Object obj3 = "this string"

I need a method which takes this object as argument, and if it is one of first 2 cases, returns single array with those elements. And if it is a last case, it returns array with single string element that came in as param.

So, if i do 

getDataForColumn(obj1) i get array: [str1, str2. str3....str5]
getDataForColumn(obj2) i get array: [str1, str2] //same as input, i know
getDataForColumn(obj3) i get array: ["this string"]

I am trying, but I really can not wrap my head how to do this with recursion, nor is it possible, well at least in this way.

This is what I came up with, and stuck.

private static Object[] getDataForColumn(Object column) {

if(column instanceof Object[]){
    Object[] castarray = (Object[])column;
        Object[]newArray = new Object[castArray.length];

    for (int i = 0; i < castarray.length; i++) {

              if((castarray[i] instanceof Object[])){
                 //recursion, but how :D    
                  }
               else{
                        newArray[i] = castArray[i];     
        }
    }
      return newArray;
   }    
 return new array with object that came in.....
}

Please help. Thanx

Upvotes: 0

Views: 430

Answers (4)

Chris
Chris

Reputation: 7855

I recommend to use an ArrayList to sequentially add all the flattened arrays together. You could have created one Array merging the current "result"-Array and the Array returned by the recursive call but using the ArrayList makes it easier. This way you don't have to iterate both Arrays and put them together in one Array.

private static Object[] getDataForColumn(Object column) {
ArrayList results = new ArrayList();

if(column instanceof Object[]){

    Object[] castarray = (Object[])column;

    for (int i = 0; i < castarray.length; i++) {

          if((castarray[i] instanceof Object[])){
             results.addAll(Arrays.asList(getDataForColumn(castarray[i])))    
           }
           else{
             results.add(castarray[i]);    
           }
    }
    return results.toArray();
}

I did not test this but i think that should work!

Hope that helps.

Upvotes: 1

Nettogrof
Nettogrof

Reputation: 2136

yes it's possible, maybe not the best way.

private static Object[] getDataForColumn(Object column) {
    if(column instanceof Object[]){
       Object[] castarray = (Object[])column;
       Object[] newArray = new Object[castArray.length];

       for (int i = 0; i < castarray.length; i++) {
          newArray[i] = getDataForColumn(castarray[i]);
       }

    } else {
       String[] newArray = {column};
    }
    return newArray;
}

I didn't test it, but I hope that will give you the idea

Upvotes: 0

duduamar
duduamar

Reputation: 3924

Here's a simple one to do it. I use List because I prefer it on arrays, but of course you can make a wrapper that will convert it to array in the end:

public static List<String> flat(Object o)
{
    List<String> strings = new ArrayList<String>();
    if (o.getClass().isArray())
    {
        Object[] oarr = (Object[]) o;
        for (Object obj : oarr)
        {
            strings.addAll(flat(obj));
        }
    }
    else
    {
        strings.add(o.toString());
    }
    return strings;
}

Upvotes: 1

amit
amit

Reputation: 178421

getDataFromColumn(Object column) {
  List<String> list = new LinkedList<String>();
  recGetData(column,list);
  return list.toArray();
}
public void recGetData(Object column,List<String> list) {
  if (column instanceof String) {
     list.add((String)column);
  } else {
     for (Object o : (Object[])column) { 
      recGetData(o,list);
     }
  }
}

hope that what you meant.
didn't test it yet, but should work....

Upvotes: 1

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