How to Print Floyd's Triangle in Java – For Loop, While Loop & Function

In this tutorial, you will learn how to print Floyd's Triangle in Java using nested loops. Floyd's Triangle is a right-angled triangular pattern of natural numbers, named after Robert W. Floyd.

For example, if the number of rows is 4, the Floyd's Triangle will look like this:

1
2 3
4 5 6
7 8 9 10

You are given a number n and the task of the program is to Print Floyd's Triangle up to n rows.

What is Floyd's Triangle?

Floyd's Triangle is a right-angled triangular arrangement of natural numbers. It starts with 1 in the first row, then 2 3 in the second row, 4 5 6 in the third row, and so on. Each row contains exactly as many numbers as its row number.

Key properties of Floyd's Triangle:

  • The first row has 1 number.
  • The second row has 2 numbers.
  • The nth row has n numbers.
  • Numbers are filled sequentially from left to right, top to bottom.

Method 1: Floyd's Triangle in Java Using Nested For Loop

This is the most common and straightforward method. We use two nested for loops — the outer loop controls the rows and the inner loop prints the numbers in each row.

import java.util.Scanner;

public class FloydTriangle
{
    public static void main(String args[])
    {
        int n, num = 1, c, d;
        Scanner in = new Scanner(System.in);
        System.out.println("Enter the number of rows of Floyd's triangle");
        n = in.nextInt();
        System.out.println("Floyd's triangle :-");
        for ( c = 1 ; c <= n ; c++ )
        {
            for ( d = 1 ; d <= c ; d++ )
            {
                System.out.print(num + " ");
                num++;
            }
            System.out.println();
        }
    }
}

Output

Enter the number of rows of Floyd's triangle
4

Floyd's triangle :-
1
2 3
4 5 6
7 8 9 10

Explanation:

  • num starts at 1 and keeps incrementing for every number printed.
  • The outer loop c runs from 1 to n, controlling the row number.
  • The inner loop d runs from 1 to c, printing exactly c numbers per row.
  • System.out.println() moves to the next line after each row.

Method 2: Floyd's Triangle in Java Using While Loop

We can also print Floyd's Triangle using a while loop. The logic is the same, only the loop syntax changes.

import java.util.Scanner;

public class FloydTriangleWhile
{
    public static void main(String[] args)
    {
        int n, num = 1, c = 1, d;
        Scanner in = new Scanner(System.in);
        System.out.println("Enter the number of rows of Floyd's triangle");
        n = in.nextInt();
        System.out.println("Floyd's triangle :-");
        while ( c <= n )
        {
            d = 1;
            while ( d <= c )
            {
                System.out.print(num + " ");
                num++;
                d++;
            }
            System.out.println();
            c++;
        }
    }
}

Output

Enter the number of rows of Floyd's triangle
4

Floyd's triangle :-
1
2 3
4 5 6
7 8 9 10

Explanation: The outer while loop handles the rows and the inner while loop prints numbers in each row. The variable num is incremented continuously to fill numbers sequentially.

Method 3: Floyd's Triangle in Java Using a Function

In this method, we move the logic into a separate function to make the code cleaner and reusable.

public class FloydTriangleFunction
{
    public static void printFloyd(int n)
    {
        int num = 1;
        for (int c = 1; c <= n; c++)
        {
            for (int d = 1; d <= c; d++)
            {
                System.out.print(num + " ");
                num++;
            }
            System.out.println();
        }
    }

    public static void main(String[] args)
    {
        int rows = 5;
        System.out.println("Floyd's triangle for " + rows + " rows:");
        printFloyd(rows);
    }
}

Output

Floyd's triangle for 5 rows:
1
2 3
4 5 6
7 8 9 10
11 12 13 14 15

Explanation: The printFloyd(int n) method takes the number of rows as a parameter and prints the triangle. This approach keeps the main() method clean and makes the logic reusable.

Comparison of All Methods

Method	Loop Type	Ease of Use	Best For
Nested For Loop	For Loop	Easy	Beginners
While Loop	While Loop	Easy	While loop practice
Using Function	For Loop	Moderate	Clean & reusable code

Frequently Asked Questions

Q1. What is Floyd's Triangle in Java?
Floyd's Triangle is a right-angled triangular arrangement of natural numbers where the first row has 1 number, the second row has 2 numbers, and so on up to n rows.

Q2. How many numbers are in the nth row of Floyd's Triangle?
The nth row always contains exactly n numbers. The total numbers printed for n rows is n*(n+1)/2.

Q3. What type of loop is used to print Floyd's Triangle?
Floyd's Triangle is printed using nested loops — an outer loop for rows and an inner loop for columns. Both for loop and while loop can be used.

Q4. What is the time complexity of Floyd's Triangle program?
The time complexity is O(n²) because of the two nested loops, where n is the number of rows.

Conclusion

In this tutorial, you learned how to print Floyd's Triangle in Java using three different methods — nested for loop, while loop, and a function. The nested for loop method is the most commonly used and easiest to understand for beginners.

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