Java Using For Loop while handling Array to make Pattern

Question

If I want to print the pattern below, and I have an Array:

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

This is what I have so far:

public static void main(String[] args) {
    int[] p = {7,5,3,1,3,5,7};

    for (int i=0; i <= 7; i++) {
        System.out.print("\n");
        for (int k =i; k <= 7; k++) {
             k = p[i];  
             // I'm trying to find a way to print "*"s with array element value
             for(int j=i; j <= 7; j++) {
                 System.out.print("*");
             }
        }
    }
}

I definitely went wrong somewhere, and I apologize for my ignorant. I'm just trying to learn. Thanks!

First of all you should use ' < ' in for loop instead of ' <= ' because you have 7 elements from 0 to 6 not eight from 0 to 7 :) — Emil Hotkowski
– Emil Hotkowski, Commented May 29, 2017 at 5:30
personally, I won't store the values in an array. Think about it this way, if stars = 7 then spaces = 0. when stars are reduced by 2, spaces are increased by one. until stars are 1, then reverse. — Bill F
– Bill F, Commented May 29, 2017 at 5:32
@MichaelMarkidis Are you coming from a C background? In Java, typically we place the opening brackets on the same line as the construct. — Tim Biegeleisen
– Tim Biegeleisen, Commented May 29, 2017 at 6:00
You are out of bounds on your Array. Inner loop. Zero based indexing. — Abstraction is everything.
– Abstraction is everything., Commented May 31, 2017 at 19:17

Michael Markidis · Accepted Answer · 2017-05-29 05:53:35Z

1

Try this out:

int [] p = { 7, 5, 3, 1, 3, 5, 7 };

// as mentioned in the comment, you want < here and not <=
for (int i = 0; i < p.length; i++)
{
    // total number of spaces needed
    int numSpaces = p[0] - p[i];

    // this array will hold the '*'s
    char [] arr = new char[p[i]];

    // half the spaces for each side
    char [] spaces = new char [numSpaces / 2];

    // fill the arrays
    Arrays.fill(arr, '*');
    Arrays.fill(spaces, ' ');

    // build the string
    StringBuilder sb = new StringBuilder();
    sb.append(spaces);
    sb.append(arr);
    sb.append(spaces);

    System.out.println(sb);
}

Output:

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

edited May 29, 2017 at 5:53

answered May 29, 2017 at 5:41

Michael Markidis

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1 Comment

Trey Truong Over a year ago

Thank you! this is really easy to understand.

Tim Biegeleisen · Accepted Answer · 2017-05-29 05:56:43Z

1

Consider the following solution which builds your output string by making one pass through all distinct star patterns. Appreciate that because your pattern is symmetric, we only need to generate one half of it, as the other half is simply a mirror image.

String top = "";
String bottom = "";
int maxStars = 7;
for (int i=0; i < maxStars; i=i+2) {
    StringBuilder line = new StringBuilder();
    for (int j=0; j < i/2; ++j)          line.append(" ");  // left spaces
    for (int j=0; j < maxStars - i; ++j) line.append("*");  // stars
    for (int j=0; j < i/2; ++j)          line.append(" ");  // right spaces
    top += line + "\n";
    // this if check prevents us from adding the single star row twice
    if (maxStars - i > 1) {
        bottom = line + "\n" + bottom;
    }
}
String pattern = top + bottom;
System.out.println(pattern);

Output:

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

Demo here:

Rextester

edited May 29, 2017 at 5:56

answered May 29, 2017 at 5:49

Tim Biegeleisen

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1 Comment

Trey Truong Over a year ago

genius. i like it.

BHAR4T · Accepted Answer · 2017-05-29 07:41:49Z

1

public static void main(String[] args) {

    int[] p = { 7, 5, 3, 1, 3, 5, 7 };

    for (int i = 0; i < p.length; i++) {
        for(int k=p[0]-p[i], m = 0;m<k;m++)    System.out.print(" ");
        for( int j = 0; j<p[i]; j++)           System.out.print(" *");
        System.out.println();
    }}

OUTPUT

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

edited May 29, 2017 at 7:41

answered May 29, 2017 at 5:56

BHAR4T

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2 Comments

Tim Biegeleisen Over a year ago

Your outer for loop had the wrong bounds, but I corrected it +1

Trey Truong Over a year ago

I am a beginner so I really love this solution. it is easy to understand for me. Thanks!

FieryCat · Accepted Answer · 2017-05-29 05:30:01Z

0

Use string-repeat in that case:

String.join('', Collections.nCopies(p[i], '*'));

or

StringUtils.repeat('*', p[i]);

answered May 29, 2017 at 5:30

FieryCat

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Comments

Abhishek · Accepted Answer · 2017-05-29 05:50:24Z

0

Try This Logic Work Fine With Your Requirements

public class Test {

public static void main(String[] args) {

int[] p = {7,5,3,1,3,5,7};

    for (int i = 0; i < p.length; i++) {

        int temp = p[i];

        if (i <= p.length/2) {

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

                System.out.print(" ");

            }

        } else {

            for (int whiteSpace = p.length - i - 1; whiteSpace > 0; whiteSpace--) {

                System.out.print(" ");

            }


        }

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

            System.out.print("*");

        }

        System.out.println("");



    }

}

**Output : **

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

answered May 29, 2017 at 5:50

Abhishek

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1 Comment

Trey Truong Over a year ago

I like how you declare temp. It's really handy, and I'll definitely use it in the future.

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