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Print Alphabet Diamond in Java

intermediate· Patterns · Character Patterns

Problem

A diamond is just a pyramid immediately followed by that same pyramid's upside-down mirror, with the shared widest row printed only once at the seam.

Given a number of rows for its top half, print a diamond shape where each row is filled with a single letter of the alphabet.

Input

5

Output

    A
   B B B
  C C C C C
 D D D D D D D
E E E E E E E E E
 D D D D D D D
  C C C C C
   B B B
    A

Java Program

Java

public class AlphabetDiamond {
    static void printRow(int i, int n) {
        char letter = (char) ('A' + i - 1);
        StringBuilder row = new StringBuilder();
        for (int s = 0; s < n - i; s++) row.append(" ");
        for (int j = 0; j < 2 * i - 1; j++) {
            if (j > 0) row.append(" ");
            row.append(letter);
        }
        System.out.println(row);
    }

    public static void main(String[] args) {
        int n = 5;

        for (int i = 1; i <= n; i++) printRow(i, n);
        for (int i = n - 1; i >= 1; i--) printRow(i, n); // skip n itself, already printed above
    }
}

▶ Run Code

Output

    A
   B B B
  C C C C C
 D D D D D D D
E E E E E E E E E
 D D D D D D D
  C C C C C
   B B B
    A

Core Logic

Pulling the per-row letter-and-spacing logic out into its own method means the diamond's top half and bottom half can both call it, just counting in opposite directions.

How It Works

1printRow(i, n) builds one row exactly the way Alphabet Pyramid does — n - i leading spaces, then letter 'A' + i - 1 repeated 2 * i - 1 times.
2The top half calls printRow(i, n) for i from 1 to n, growing the pyramid up to its widest row.
3The bottom half calls it again for i from n - 1 down to 1, mirroring the top half without repeating the widest row.
4Because both halves share one method, the diamond's two sides can never drift out of sync with each other.

For n = 5, the top half prints rows for letters A through E; the bottom half then prints D down through A, mirroring everything except the shared E row.

💡

Key Point: The bottom half starts at n - 1, not n — repeating the widest row would print it twice at the seam where the two halves meet.

Complexity

Time Complexity: O(n²)Space Complexity: O(1)

Why: Both halves together print a number of characters proportional to n², the same growth rate as a single pyramid, just doubled.

Print Alphabet Diamond in Java

Problem

Java Program

Output

Core Logic

Key Concepts

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