Print Fibonacci series in a diamond shape (Using Java)

Question:: The user will enter the number and the output should contain those many rows printing the Fibonacci (Exactly as shown in the below examples).

Example: 

Input :7 (Number of rows)

Output:

                                1

                              1+2

                            3+5+8

                          13+21+3

                            4+55+

                              89+

                                1

Note: To form a prefect diamond split the numbers of the Fibonacci series to next row and for the last number of the Fibonacci series, discard any remaining digit after the split, to print a prefect diamond shape (In example: "34" was split to place "4" into the next row to form a diamond and "144" is split place "1" in the last row and remaining digit "44" is discarded).

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class FibonacciSeriesInDiamondShape {

 // Formula for the n-th Fibonacci number
 private static int fibonacci(int n) {
  if (n == 1) {
    return 1;
  }
  if (n == 2) {
   return 1;
  }
  return fibonacci(n - 1) + fibonacci(n - 2);
  }

  // returns a string of all Fibonacci numbers upto the nth Fibonacci number  concatenated with "+"
  private static String concatFibSeries(int n) {
   StringBuilder sb = new StringBuilder();
   for (int i = 1; i <= n; i++) {
     sb.append(fibonacci(i)).append("+");
   }
   return sb.toString();
  }

  // cuts the string returned by the method concatFibSeries(int n) into small
  // chunks returns a list of strings with list.size equal to given rows the
  // length of the strings beginns by one and increases by two on each step
  // till the middle row is reached and decreases by two till the end of rows is reached
  private static List chopper(String concatenatedString, int rows) {
   List list = new ArrayList<>();
   for (int i = 1, j = 1; i <= rows; i++, j = (i <= Math.ceil(rows / 2.)) ? j + 2 : j - 2) {
     list.add(concatenatedString.substring(0, j));
     concatenatedString = concatenatedString.substring(j);
     if (concatenatedString.startsWith("+")) {
       concatenatedString = concatenatedString.substring(1);
     }
   }
   return list;
  }

  // adds the required space before and after each string and prints the string
   private static void printDiamond(List list) {
    final int listSize = list.size();
     for (int i = 0; i < listSize; i++) {
      String str = "";
      for (int j = 0; j < (Math.abs(list.size() - Math.ceil(list.size() / 2.) - i)); j++) {
        str += " ";
      }
      System.out.println(str + list.get(i) + str);
    }
  }

  public static void main(String[] args) {
   try (Scanner scanner = new Scanner(System.in);) {
    System.out.println("Enter number of rows:");
    int noOfRows = scanner.nextInt();
    String str = concatFibSeries(noOfRows * 2);
    List list = chopper(str, noOfRows);
    printDiamond(list);
    }
  }
}