Java Program to Print Downward Right Triangle Star Pattern

In this program we print a downward right triangle of stars. The first row has five stars, and each row after it has one star fewer.

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.

1. The Pattern

For 5 rows the program prints:

* * * * *
* * * *
* * *
* *
*

2. How the Program Works

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

• The outer loop counts row down from numberOfRows to 1, so the longest row comes first.
• The inner loop prints row stars, each followed by a space.
• System.out.println() moves to the next line after each row.

3. Java Program

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

        // outer loop for the rows, counting down
        for (int row = numberOfRows; row >= 1; row--) {
            // inner loop to print the stars
            for (int column = 1; column <= row; column++) {
                System.out.print("* ");
            }
            // move to the next line
            System.out.println();
        }
    }
}

* * * * *
* * * *
* * *
* *
*

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 DownwardRightTriangleStarPatternInput {
    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, counting down
        for (int row = numberOfRows; row >= 1; row--) {
            // inner loop to print the stars
            for (int column = 1; column <= row; column++) {
                System.out.print("* ");
            }
            // move to the next line
            System.out.println();
        }
    }
}

Enter the number of rows: 6
* * * * * *
* * * * *
* * * *
* * *
* *
*

5. Summary

• The outer loop picks the row; the inner loops print the spaces and the stars for that row.
• Work out how many spaces and stars each row needs, then write one inner loop for each.
• Keep numberOfRows in a variable, so the same program can print the pattern in any size.

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