Java Program to Print Right Triangle Character Pattern - 3

In this program we print a right triangle where every row repeats one letter: row 1 prints A once, row 2 prints B twice, and so on.

Like every pattern program, it is built from nested loops: the outer loop picks the row, and the inner loops print what goes on that row. Java stores a char as a number, so adding to 'A' and casting back with (char) gives the following letters.

1. The Pattern

For 5 rows the program prints:

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

2. How the Program Works

Here is what each printed line is made of when numberOfRows is 5:

• The outer loop runs once for each row, from 1 to numberOfRows.
• letter is the letter for the row: A for row 1, B for row 2, and so on.
• The inner loop prints letter row times.
• System.out.println() moves to the next line after each row.

3. Java Program

public class Pattern3 {
    public static void main(String[] args) {
        int numberOfRows = 5;

        // outer loop for the rows
        for (int row = 1; row <= numberOfRows; row++) {
            char letter = (char) ('A' + row - 1);
            // inner loop to print the row letter, row times
            for (int column = 1; column <= row; column++) {
                System.out.print(letter + " ");
            }
            // move to the next line
            System.out.println();
        }
    }
}

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

4. Print the Pattern for Any Number of Rows

To let the user choose the size of the pattern, read the number of rows with a Scanner. The loops stay the same.

import java.util.Scanner;

public class Pattern3Input {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter the number of rows: ");
        int numberOfRows = scanner.nextInt();
        scanner.close();

        // outer loop for the rows
        for (int row = 1; row <= numberOfRows; row++) {
            char letter = (char) ('A' + row - 1);
            // inner loop to print the row letter, row times
            for (int column = 1; column <= row; column++) {
                System.out.print(letter + " ");
            }
            // move to the next line
            System.out.println();
        }
    }
}

Enter the number of rows: 6
A
B B
C C C
D D D D
E E E E E
F F F F F F

5. Summary

• The outer loop picks the row; the inner loops print the spaces and the letters for that row.
• (char) ('A' + k) gives the letter k places after A.
• Keep numberOfRows in a variable, so the same program can print the pattern in any size.

Related Programs

• Java Program to Print Right Triangle Character Pattern - 1
• Java Program to Print Right Triangle Character Pattern - 2
• Java Program to Print Left Triangle Character Pattern - 1
• Java Program to Print Left Triangle Character Pattern - 2
• All Java Pattern Programs