Print Downward Triangle Star Pattern in Java

In this article, we will understand how to print a downward triangle star pattern using Java. This pattern is created with multiple for loops and print statements.  We will learn through two examples: one where the user inputs the number of rows, and another where the number of rows are predefined in the program.

Problem Statement

Write a Java program to print downward triangle star pattern. Below is a demonstration of the same ?

Input

Enter the number of rows : 8

Output

The downward triangle star pattern :
* * * * * * * *
 * * * * * * *
  * * * * * *
   * * * * *
    * * * *
     * * *
      * *
       *

Using user based input

Below are the steps to print a downward triangle star pattern using user-based input ?

• Import the Scanner class by using java.util package.
  
• Create a scanner object to read the number of rows from the user.
  
• Prompt the user to input the number of rows (denoted as my_input).
  
• Loop to print spaces and stars:
  
• The outer loop (i) runs for each row.
  
• The first inner loop (j) prints spaces.
  
• The second inner loop (k) prints stars with a space between them.
  
• Display the downward triangle based on user input.
  

Example

Here, the input is being entered by the user based on a prompt ?

import java.util.Scanner;
public class DownwardTriangle{
   public static void main(String args[]){
      int i, j, k, my_input;
      System.out.println("Required packages have been imported");
      Scanner my_scanner = new Scanner(System.in);
      System.out.println("A reader object has been defined ");
      System.out.print("Enter the number of my_input : ");
      my_input = my_scanner.nextInt();
      System.out.println("The downward triangle star pattern : ");
      for ( i= 0; i<= my_input-1; i++){
         for ( j=0; j<=i; j++){
            System.out.print(" ");
         }
         for ( k=0; k<=my_input-1-i; k++){
            System.out.print("*" + " ");
         }
         System.out.println();
      }
   }
}

Output

Required packages have been imported
A reader object has been defined
Enter the number of my_input : 8
The downward triangle star pattern :
* * * * * * * *
 * * * * * * *
  * * * * * *
   * * * * *
    * * * *
     * * *
      * *
       *

Using previously defined input

Following are the steps to print a downward triangle star pattern ?

• Define an integer variable (my_input) for the number of rows.
  
• Display the number of rows and the downward triangle star pattern on the console.
  
• Loop to print spaces and stars:
  
• The outer loop (i) runs for each row.
  
• The first inner loop (j) prints spaces.
  
• The second inner loop (k) prints stars with a space between them.
  
• Display the downward triangle based on predefined input.
  

Example

Here, the integer has been previously defined, and its value is accessed and displayed on the console ?

public class DownwardTriangle{
   public static void main(String args[]){
      int i, j, k, my_input;
      my_input = 8;
      System.out.println("The number of rows is defined as " +my_input);
      System.out.println("The downward triangle star pattern : ");
      for ( i= 0; i<= my_input-1; i++){
         for ( j=0; j<=i; j++){
            System.out.print(" ");
         }
         for ( k=0; k<=my_input-1-i; k++){
            System.out.print("*" + " ");
         }
         System.out.println();
      }
   }
}

Output

The number of rows is defined as 8
The downward triangle star pattern :
* * * * * * * *
 * * * * * * *
  * * * * * *
   * * * * *
    * * * *
     * * *
      * *
       *