Java Program to Print Downward Triangle Star Pattern

Downward triangle star pattern means we want to print a triangle that is downward facing means base is upwards and by default, orientation is leftwards so the desired triangle to be printed should look like

* * * *
* * *
* *
*

Example

Java

// Java Program to Print Lower Star Triangle Pattern

// Main class
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        // Nested 2 for loops for iteration over the matrix

        // Outer loop for rows
        int rows = 9;
        for (int a = rows - 1; a >= 0; a--) {

            // Inner loop for columns
            for (int b = 0; b <= a; b++) {

                // Prints star and space
                System.out.print("*"
                                 + " ");
            }

            // By now we are done with single row so new
            // line
            System.out.println();
        }
    }
}

Output

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

Using Recursion

Java

// added by Manish Sharma

import java.io.*;

class GFG
{
      public static void printRow(int n)
    {
        if(n == 0) // base case
        {
             return;
        }

          System.out.print("* ");
          printRow(n - 1); // next * in the same row
    }
      public static void nextRow(int n)
    {
        if(n == 0)
        {
            return;
        }
          printRow(n); // prints the whole row recursively.
        System.out.print("\n"); // for new line after printing a row...
          nextRow(n - 1);     // changed to new row
    }

    public static void main (String[] args)
    {
        GFG.nextRow(5); // no need to create an object of GFG class as nextRow method is static.
    }
}

Output

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

Time Complexity: O(n²), where n represents the given number of rows.
Auxiliary Space: O(1), no extra space is required, so it is a constant.