Dividing a string into 3 parts and export to CSV in JAVA

I have a string "1 kg potatoes" whereas 1 is the quantity, kg is the unit and potatoes is the item. I want that the compiler will read a string and match with "unit_list & quantity_list"(see code below). And it saves the results into 3 columns in a CSV file.

   List<String> unit_list = Arrays.asList("g", "kg","ml","l");          
   List<String> quantity_list = Arrays.asList("Full", "Quarter", "Half", "3 Quarter", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0");                                                                                                   
                                                                                                                                                                                                                                                               
   String input = "1 kg potatoes";                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
                                                                                                                                                                            
   if (unit_list.equals(input)) {                                                                                                                                                                                                               
       System.out.println("Unit Detected");                                                                                                                                                                                                                    
   }  
                                                                                                                                                                                                                                                         
   if (quantity_list.equals(input)) {                                                                                                                                                                                                    
       System.out.println("Quantity Detected");                                                                                                                                                                                                                
   }                                                                                                                                                                                                                                                           

>Expected Output in CSV File
>
>Quantity, Unit, Item
>
>1, kg , potatoes

But this is not working for me. Please help me to do this.

EDIT: Based on the fact that you said something like "8 g carrots" could be "8g carrots" I've updated the original code and added a new method to the bottom.

Here's the solution I came up with. Since you said order is not guaranteed, and we don't need to check if the "item" is valid, I did it this way:

  public static void parseToCSV() throws IOException {
    List<String> list = generateList();
    List<String> unitList = Arrays.asList("g", "kg","ml","l");          
    List<String> quantityList = Arrays.asList("Full", "Quarter", "Half", "3 Quarter", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0");                                                                                                   

    for(String s : list) {
      String[] strArr = s.split(" ");
      // Checks if the String array is too short for what we need(i.e "8g carrots" instead of "8 g carrots")
      if(strArr.length == 2) {
        String newStr = rewriteString(strArr, quantityList);
        strArr = newStr.split(" ");
      }
      String[] itemLine = new String[3];
      for(int i = 0; i < strArr.length; i++) {
        String str = strArr[i];
        int index = findValueLocation(str, quantityList, unitList);
        itemLine[index] = str;
      }
      String line = createLineForCSV(itemLine);
      writeToFile(line);
    }

  }
  
  private static List<String> generateList() {
    List<String> list = new ArrayList<>();
    String inputOne = "1 kg potatoes";
    String inputTwo = "3 g juice";
    String inputThree = "8g carrots";
    list.add(inputOne);
    list.add(inputTwo);
    list.add(inputThree);
    return list;
  }
  
  /**
   * Return the index where the value should go in a comma separated String. If the
   * value is not found in either list then it is the item by default.
   */
  private static int findValueLocation(String str, List<String> quantityList, List<String> unitList) {                                                                                                 
    
    for(String quantity : quantityList) {
      if(quantity.equals(str)) {
        return 0;
      }
    }
    for(String unit : unitList) {
      if(unit.equals(str)) {
        return 1;
      }
    }
    return 2;
  }
  
  private static String createLineForCSV(String[] itemLine) {
    StringBuilder sb = new StringBuilder();
    sb.append(itemLine[0]).append(",");
    sb.append(itemLine[1]).append(",");
    sb.append(itemLine[2]);
    return sb.toString();
  }
  
  private static void writeToFile(String line) throws IOException {
    // Set to true for append mode
    BufferedWriter writer = new BufferedWriter(new FileWriter("csv_file.csv", true));
    writer.write(line);
    writer.newLine();
    writer.close();
  }

This works when I tested it. The only thing is it will always append to the CSV file every time you run it. If you want an option to clear the file so you can write all the data fresh then you could just add this method:

  private static void clearFile() throws IOException {
    FileWriter writer = new FileWriter("csv_file.csv", false);
    writer.write("");
    writer.close();
  }

EDIT: New method to fix issue of "8g" instead of "8 g". What this does is check if the split String has length of 2. If so then it is not separated properly. We check the quantityList, since it should never come as "g8 carrots". We find the quantity, and create a new string of <Quantity><space><Rest of String><space><Other String> and return that as the properly made String. Kind of a hacky solution, but it works for me.

  private static String rewriteString(String[] arr, List<String> quantityList) {
    String strOne = arr[0];
    String strTwo = arr[1];
    String newStr = "";
    for(String quantity : quantityList) {
      if(strOne.contains(quantity)) {
        // 8g carrots becomes "8 g carrots"
        newStr = quantity + " " + strOne.substring(quantity.length()) + " " + strTwo;
        break;
      } else if(strTwo.contains(quantity)) {
        newStr = quantity + " " + strTwo.substring(quantity.length()) + " " + strOne;
        break;
      }
    }
    return newStr;
  }

I hope this helps!