How to print Floyd's Triangle in Java with Example

By: Khondoker Hafizur Rahman on 2:16 AM

There are lots of
programming exercise in Java, which involves printing a particular pattern in
console, one of them is printing Floyd triangle in console. In Floyd triangle
there are n integers in the nth row and a total of (n(n+1))/2
integers in n rows. This is one of the most simple pattern to print but helpful
in learning how to create other more complex patterns. Key to develop pattern
is using nested loops and methods
like System.out.print() and println() appropriately. Actually pattern based
programming task are originally designed to master loops in programming. A good
programmer should be able to look a pattern and break into nested loops. A more
formal definition of Floyd's triangle : "It's a right angled triangle of
array of natural numbers, which is named after Robert Floyd. It is defined by
filling the rows of the triangle with consecutive numbers, stating with 1 in
the top left corner".



It looks like following pattern :

1

2  3

4  5  6

7  8  9  10

11  12  13  14  15

Your task is to print this table using nested loops in Java. Main point is to
build the logic by yourself, this will help you a lot in the long run.

Java Program to draw Floyd's Triangle

Here is my sample code example to draw
format representing Floyd's triangle. This  program first ask user to
enter number of rows till you want to show Floyd's triangle. You can use Scanner to get the input from user
and then you can use that number in your logic. The code for printing Floyd's
triangle is the method printFloydTriangle(int
rows), it takes number of
rows, which is the user input. This method uses nested loops, two loop in this
case to draw format of Floyd's triangle. First loop is used to print number of
rows and second loop is used to print numbers in the row.

import java.util.Scanner;

/**

* Java program to print
Floyd's triangle up-to a given row

*

* @author Javin Paul

*/

public class FloydTriangle {

    public static void main(String args[]) {

        Scanner cmd = new Scanner(System.in);

        System.out.println("Enter the number of rows of Floyd's triangle, you want to
display");

        int rows =
cmd.nextInt();

        printFloydTriangle(rows);

    }

    /**

     * Prints Floyd's triangle of a given row

     *

     * @param rows

     */

    public static void printFloydTriangle(int rows) {

        int number = 1;

        System.out.printf("Floyd's triangle of %d rows is : %n", rows);

        for (int i = 1; i <= rows; i++) {

            for (int j = 1; j <= i; j++) {

                System.out.print(number + " ");

                number++;

            }

            System.out.println();

        }

    }

}

Output

Enter the number of rows of
Floyd's triangle, you want to
display

5

Floyd's triangle of 5 rows is :

1

2 3

4 5 6

7 8 9 10

11 12 13 14 15

Enter the number of rows of
Floyd's triangle, you want to
display

10

Floyd's triangle of 10 rows is :

1

2 3

4 5 6

7 8 9 10

11 12 13 14 15

16 17 18 19 20 21

22 23 24 25 26 27 28

29 30 31 32 33 34 35 36

37 38 39 40 41 42 43 44 45

46 47 48 49 50 51 52 53 54 55

That's all about how do you print Floyd's triangle in Java. It's a very
good programming exercise to build your foundation on loops especially nested
loops. After that you can also try couple of other pattern based programming
task's e.g. printing Pascal's triangle and some other patterns. If you like to
do solve some programming problems other than patterns you can also try
following exercises :

1.     
How
to count occurrences of  a character in String? (Solution)

2.     
How
to find first non repeated characters from String in Java? (See here for solution)

3.     
Write
a Program to check if a number is binary in Java? (Solution)

4.     
How
to remove duplicates from array without using Collection API? (Solution)

5.     
Write
a Program to calculate Sum of Digits of a number in Java? (Solution)

6.     
How to Swap Two Numbers without using Temp Variable in Java?
(Trick)

7.     
How to check if LinkedList contains loop in Java? (Solution)

8.     
Write a Program to Check if a number is Power of Two or not?
(Answer)

9.     
How to find middle element of LinkedList in one pass? (See here for Solution)

10.
How to check if a number is Prime or not? (Solution)

11.
Write a Program to calculate factorial using recursion in
Java? (Click here for solution)

12.
How to check if a number is Palindrome or not? (Solution)

13.
How to check if Array contains duplicate number or not? (Solution)

14.
How to remove duplicates from ArrayList in Java? (Solution)

15.
Write a Java Program to See if two String are Anagram of each
other? (Solution)

16.
Write a Program to find Fibonacci Series of a Given Number? (Solution)

17.
How to check if a number is Armstrong number or not? (Solution)

18.
Write a Program to prevent Deadlock in Java? (Click here for solution)

19.
Write a Program to solve Producer Consumer Problem in Java. (Solution)

20.
How to reverse String in Java without using API methods? (Solution)

21.
How to print prime factors of a number in Java?
(Solution)