Star Pattern Program in Java

This is the Java Program to Print * in Triangular Pattern.

Problem Description

Write a Java Program to Print * in Triangular Pattern, upto n lines.

Problem Solution

The idea is to use nested loops.
Iterate the first loop from 1 to n. Print the required number of spaces using a nested loop and finally display the * using a nested loop.

Program/Source Code

Here is the source code of the Java Program to Print * in Triangular Pattern. The program is successfully compiled and tested using IDE IntelliJ Idea in Windows 7. The program output is also shown below.

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//Java Program to Print * in Triangular Pattern

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import java.io.BufferedReader;
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import java.io.InputStreamReader;
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public class Pattern2 {
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    // Function to display the pattern
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    public static void main(String[] args) {

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        int i,j,k,n;
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        System.out.println("Enter the number of lines");

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

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        try{
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            n = Integer.parseInt(br.readLine());

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        }catch (Exception e){
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            System.out.println("An error occurred");

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            return;
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        }
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        System.out.println("The triangular pattern is");

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        int space = n-2;
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        for(i=1; i<=n; i++){
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            for(k=space;k>=0;k--){
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                System.out.print(" ");
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            }
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            space--;
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            for(j = 1; j<=i; j++){
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                System.out.print("* ");
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            }
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            System.out.println();
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        }
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    }
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}
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Program Explanation

1. In function main(), firstly the number of lines n is entered.
2. The outer loop for(i=1; i<=n; i++) is used to print n lines.
3. The nested loop for(k=space;k>=0;k–), is used to print the required spaces.
4. The nested loop for(j = 1; j<=i; j++), is used to print the required number of *.

Time Complexity: O(n²).

Runtime Test Cases

 
Case 1 (Simple Test Case):
 
Enter the number of lines
8
The triangular pattern is
       * 
      * * 
     * * * 
    * * * * 
   * * * * * 
  * * * * * * 
 * * * * * * * 
* * * * * * * *

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