Pattern printing in Java

[arunjib]

i want to get following out for a java program... how i should start my study?


output of the program:

How many stars you want to print in 1st row ? 7

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

[Spyderpig]

	

		System.out.println("*******");
		System.out.println(" *   * ");
		System.out.println("  * *  ");
		System.out.println("   *   ");
		System.out.println("  * *  ");
		System.out.println(" *   * ");
		System.out.println("*******");

prolly something like this

[doWhile]

Cross posted: Loops & Control Statements

[arunjib]

	

		System.out.println("*******");
		System.out.println(" *   * ");
		System.out.println("  * *  ");
		System.out.println("   *   ");
		System.out.println("  * *  ");
		System.out.println(" *   * ");
		System.out.println("*******");

prolly something like this

sorry! i need it using loops not using output stream like u explained

[sunde887]

What have you tried?

[arunjib]

What have you tried?

nothing idea till now. please start a hint i want to study...

[überfuzz]

Try something in the lines of:
for() {}
While() {}

[arunjib]

Try something in the lines of:
for() {}
While() {}

its very short hint sir, more please

[überfuzz]

No problem sir. Let's see the loop you've got so far. :)

[arunjib]

No problem sir. Let's see the loop you've got so far. :)

for(i=0;i<n;i++) //n is number of * to print in first line
{
System.out.print("*");
for(i=0;i<n-2;i++)
System.out.println();
System.out.print("*");
}
}

[sunde887]

Try thinking about it by the numbers. Look for a pattern in how the stars change.

[überfuzz]

Pseudo code, just coding from my head. You should be able to get something out of it.

//if user is going to decide size, use a scanner
control size % 2 = 1 // I think, uneven anyway.
loop i from 0 to size
   if(i == 0 && i == size)
      //print whole line
   else
      loop j from 0 to size
      if(j == i && j == size - i)
         print *
      else
         print ' '

[JosAH]

Why not use a bit of 101 mathematics? Your figure exists in a square of size n times n; think of two axes ranging from -n/2 to n/2. A star must be drawn at a position (x,y) iff:

1) y == n/2 or y == -n/2
2) y == x or y == -x

A simple method can implement this:

boolean isStar(int x, int y, int n) {
   return Math.abs(y) == n/2 || Math.abs(x) == Math.abs(y);
}

All you have to do is loop over the coordinates and print stars if they have to be printed:

for (int y= -n/2; y <= n/2; y++) {
   for (int x= -n/2; x <= n/2; x++) 
      System.out.print(isStar(x, y, n)?'*':' ');
   System.out.println();
}

et voila ...

kind regards,

Jos

[nasim_khan]

import java.io.*;
class netpat
{
public static void main(String arg[])throws IOException
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.print("How many * in first row ? : ");
int n=Integer.parseInt(br.readLine());
int i,j;
for(i=1;i<=n;i++)
{
for(j=1;j<=n;j++)
{
if(i==1 || i==n)
System.out.print("*");
else
if(i==j || i==n-j+1)
System.out.print("*");
else
System.out.print(" ");
}
System.out.println();
}
}
}

this should give you your desired output....

[sunde887]

Don't spoon feed code. When posting code, use code tags. Also, this thread is a few months old and I'd imagine to op is either long gone, or at least solved the problem already.

[nasim_khan]

Don't spoon feed code. When posting code, use code tags. Also, this thread is a few months old and I'd imagine to op is either long gone, or at least solved the problem already.

Thnx for the advice....I am new to this forum...will keep that in mind next time onwards...

[Junky]

i need it using loops

No probs.

for(int i = 0; i < 7; i++) {
    switch(i) {
    case 0:
    case 6:
        System.out.println("*******");
        break;
    case 1:
    case 5:
        System.out.println(" *   * ");
        break;
    case 2:
    case 4:
        System.out.println("  * *  ");
        break;
    case 3:
        System.out.println("   *   ");
        break;
    }
}

[DarrylBurke]

i need it using loops

No probs.

Sheesh.

for (int i = 0; i < 1; i++) {
    System.out.println("*******");
    System.out.println(" *   * ");
    System.out.println("  * *  ");
    System.out.println("   *   ");
    System.out.println("  * *  ");
    System.out.println(" *   * ");
    System.out.println("*******");
}

db

[Junky]

Let me guess Daryl, you also declare arrays with a length of 1. ;)