How to make a diamond using Nested For Loops

Question

So I was assigned to make a diamond with asterisks in Java and I\'m really stumped. Here\'s what I\'ve come up with so far:

public class Lab1 
{
   public s         


        

Answer 1

I can see what you are trying to do and this is a pretty neat way to think about the diamond.

You will have some issues with the j counter when i goes negative..look at how to use Math.abs()

Also try writing some pseudo code in basic steps with comments to get the pattern clear:

 //print 5 spaces + 1 star
 //print 4 spaces + 2 stars
 //print 3 spaces + 3 stars
 //print 2 spaces+ 4 stars
 .
 . 
 .  
 //print 5 spaces + 1 star

Then, literally substitute variables (j and i) for the numbers.

You now have a model. This is often the hardest part in programming..getting the model right. Only jump into coding when you have a good idea for how the model works.

Once you have the variables substituted, you can try to convert the whole thing into an automated loop.

Answer 2

Try this

public class Main
{
    public static void main(String[] args) {

        int n = 50;
        int space = n - 1;

        for(int i = 0; i < n; i++){

            for(int j = 0; j < space; j++) {
                System.out.print(" ");
            }

            for(int j = 0; j <= i; j++) {
                 System.out.print("* ");
            }

            System.out.println("");
            space--;
        }

        space = 0;

        for(int i = n; i > 0; i--){

            for(int j = 0; j < space; j++){

                System.out.print(" ");
            }

            for(int j = 0; j < i; j++) {
                System.out.print("* ");
            }

            System.out.println("");
            space++;
        }

    }
}

Answer 3

public class Diamond {

//Size of the diamond
private int diagonal;

public Diamond(int diagonal) {
    this.diagonal = diagonal;
}

public void drawDiamond() {
    int n = diagonal;
    for (int i = n / 2; i >= -n / 2; i--) {
        for (int k = 0; k < i; k++) {
            System.out.print(" ");
        }
        for (int j = 1; j <= (n - i * 2) && i >= 0; j++) {
            System.out.print("*");
        }
        for (int k = 1; k <= -i && i < 0; k++) {
            System.out.print(" ");
        }
        for (int j = (n / 2) * 2 + 2 * i; j >= -(n % 2 - 1) && i < 0; j--) {
            System.out.print("*");
        }
        System.out.println();
    }
}

public static void main(String[] args) {
    Diamond a = new Diamond(21);  //You pass diamond size here in the constructor
    a.drawDiamond();
}
}

The main problem is parity of diagonal. If it's even you can't properly draw top asterisk. So there is 2 types of diamonds - with even and odd diagonal (with 2 and 1 asterisk at the top).

Answer 4

package com.DiamondPrintingProgram;

import java.util.Scanner;

public class DiamondPrintingProgram {

    public static void main(String[] args) { 
        int num = getInput();
        int middle = (int) num / 2 + 1;
        printOutput(num,middle); 
    }
    public static int getInput() {
        Scanner sc = new Scanner(System.in);
        int num;
        System.out.print("Enter a odd number: ");
        while (true) {
            num = sc.nextInt();
            if (num % 2 != 0) {
                break;
            }
            System.out.print("Please Enter a ODD NUMBER: ");
        }
        return num;
    }
    private static void printOutput(int num, int middle){
        char asterisk = '*';
        for (int j = 0; j < num; j++) {
            for (int i = 1; i <= num; i++) {
                if (j < middle) {
                    if ((i < (middle - j) || i > (middle + j))) {
                        System.out.print(' ');
                    } else {
                        System.out.print(asterisk);
                    }
                } else {
                    if ((i < (j - middle + 2)) || (i > (2 * num - j - middle))) {
                        System.out.print(' ');
                    } else {
                        System.out.print(asterisk);
                    }
                }
            }
            System.out.println();
        }
    }
}

Answer 5

import static java.lang.System.out;
import java.util.Scanner;
public class Diamond {

    public static void main(String[] args) {

    Scanner sc=new Scanner(System.in);
    int row=sc.nextInt();
    sc.close();
    Diamond d=new Diamond();
    d.upperDiamond(row);
    d.lowerDiamond(row-2);

    }
    public void upperDiamond(int a){

    for(int i=0;i<a;i++){
        for(int j=a-1;j>i;j--)
            out.print(" ");
        for(int k=0;k<2*i-1;k++)
        out.print("*");
        out.print("\n");
        }
    }
    public void lowerDiamond(int b){

        for(int i=0;i<b;i++){
        for(int j=0;j<=i;j++)
        out.print(" ");
        for(int k=0;k<2*(b-i)-1;k++)
            out.print("*");
        out.print("\n");
        }
    }

}

Answer 6

public class MyDiamond
{
   public static void main(String[] args)
   {
      int numRows=151;//Length of the pyramid that we want.151 is just an example
      int midrow = (numRows+1)/2;//midrow is the middle row and has numRows number of *

      int diff=0;
      for(int i=1;i<numRows+1;i++)
      {
         for(int j=1;j<numRows+1;j++)
         {
            if(((midrow-diff)<=j && (j<=midrow+diff)))
            {
               System.out.print("*");
            }else
            {
               System.out.print(" ");
            }

         }
         System.out.println();
         if(i<midrow)
         {
         diff++;
         }else
         {
            diff--;
         }
      }




   }

}