Butterfly Pattern in Java

In this section, we will understand how to create a Java program to pint the Butterfly Pattern. It is frequently asked by the interviewers to check the logical thinking of the of the candidate.

In order to implement the logic for Butterfly Pattern, we take input N from the user and then we print it over N rows.

Let's implement the code for printing the Butterfly Pattern in Java.

ButterFlyPatternExample.java

// import required classes
import java.util.Scanner;
// create class ButterFlyPatternExample to design butterfly pattern
public class ButterFlyPatternExample {
	// create drawButterflyPattern() method that will print Butterfly over n rows
	public static void drawButterflyPattern(int N) {
		// declare and initialize variables that helps to print Butterfly pattern
		int space = 2*N-1;
		int star = 0;
		// use for loop 
        		for(int j = 1; j <= 2*N-1; j++){
            			if(j <= N){
                			space = space - 2;
                			star++;
            			}
            			else {
                			space = space + 2;
                			star--;
            			}
			// use for loop to print star
            			for(int m = 1; m <= star; m++){
               			 System.out.print("*");
            			}
			// use for loop to print space
            			for(int n = 1; n <= space; n++){
                			System.out.print(" ");
            			}
			// use for loop to print star for special case
            			for(int p = 1; p <= star; p++){
                			if(p != N){
					System.out.print("*");
				}
            			}
            			System.out.println();
        		}
	}
	// main() method start
    	public static void main(String[] args) {
		int N;
		// create Scanner class object to take input from user
       		 Scanner sc = new Scanner(System.in);
        		System.out.println("Enter value of N");
		N = sc.nextInt();
		// close scanner class object
		sc.close();
		// call drawButterflyPattern() method 
		drawButterflyPattern(N);
    	}
}

Output:

ButterflyPatternExampleNew.java

//import required classes
import java.util.Scanner; 
//create class ButterflyPatternExampleNew to design butterfly pattern
public class ButterflyPatternExampleNew {
	// main() method start
 	public static void main(String[] args) {
		int N;
		// create Scanner class object to take input from user
    		Scanner scan = new Scanner(System.in);
     		System.out.println("Enter value of N");
		N = scan.nextInt();
		
		// call drawButterflyPattern() method of class ButterflyPattern
		ButterflyPattern obj = new ButterflyPattern();
		obj.drawButterflyPattern(N);
		
		// close scanner class object
		scan.close();
		
 	}
}
// create a separate class ButterflyPattern
class ButterflyPattern{
	
	// create user-defined method that will draw butterfly pattern
	public void drawButterflyPattern(int N) {
		
		// declare and initialize variables that helps to print Butterfly pattern
		int space = 2*N-1;
		int star = 0;
		
		// use for loop 
 		for(int j = 1; j <= 2*N-1; j++){
     			if(j <= N){
         			space = space - 2;
         			star++;
     			}
     			else {
         			space = space + 2;
         			star--;
     			}
		// use for loop to print star
     			for(int m = 1; m <= star; m++){
        			 System.out.print("*");
     			}
		// use for loop to print space
     			for(int n = 1; n <= space; n++){
         			System.out.print(" ");
     			}
		// use for loop to print star for special case
     			for(int p = 1; p <= star; p++){
         			if(p != N){
				System.out.print("*");
			}
     			}
     			System.out.println();
 		}
	}
}

Output: