Alternate * and # pattern

We do not do your HomeWork.
HomeWork is not set to test your skills at begging other people to do your work, it is set to help your teacher to check your understanding of the courses you have taken and also the problems you have at applying them.
Any failure of you will help your teacher spot your weaknesses and set remedial actions.
So, give it a try, reread your lessons and start working. If you are stuck on a specific problem, show your code and explain this exact problem, we might help.

Quote:

That's not my homework.
I got it while solving an online quiz code and I couldn't do it.

It is HomeWork because it is complicated only for newbie student, it is aimed to teach you how to combine things.

Advice:
Take a sheet of paper and make a table where you report facts in columns.
- line number
- line number is odd or even
- how many stars on the line
- how many # on the line
- starts on left or right
Make this table for 8 and 9, then look for patterns.

Training exercises:
Ask a number, then draw something:
-Draw a triangle
*
* *
* * *
* * * *
* * * * *
-Add # to make it a square
* # # # #
* * # # #
* * * # #
* * * * #
* * * * *
-Swap left-right
# # # # *
# # # * *
# # * * *
# * * * *
* * * * *
-Draw a pyramid
*
* *
* * *
* *
*
-Add # to make it a square
* # # # #
* * # # #
* * * # #
* * # # #
* # # # #
-Swap left-right
# # # # *
# # # * *
# # * * *
# # # * *
# # # # *

Being a programmer is also being at ease with mathematics
Check the behavior of the absolute function
For x= -2, -1, 0, 1 and 2 :
what is the result of abs(x)
what is the result of 3-abs(x)
Compare with the other patterns.

While it seems most aspects are being answered in the other solutions already, here's some more general advice on how to decipher the algorithm that determines the output.

You have to investigate all the examples to recognize the pattern. The longest example (in this case for the input 8) will typically provide the most information. If you think you can spot a property of the longest pattern, you can check the other examples to see if your conjecture holds.

Then you can check how the patterns depend on the input value. Again, if you think you can spot a dependency, check all examples to find out if you're right.

Each of the properties and dependencies that you found can be translated into a rule and incorporated into your program. Depending on the complexity of the pattern, it may require a lot of rules. If you think you've found them all, you can try to complete your program. However, if you find that your program is lacking information to correctly reproduce the patterns, you probably missed a rule and you need to check the examples again.

Alternately you can start writing your program and, while doing so, consider how much and what information you may need to reproduce each line of output. E. g. how many lines do you need to print, how long is each output line, what does a particular line consist of, etc.. Then you can look for clues on that specific information in the examples.

public class Program
{
    public static void main(String[] args) {
        int k,i,j,n=3;
        int sc,hc;
        sc=1;
        hc=n-1;
        
        for(k=0;k<n;k++)
        {
            if(k%2==0)
            {
                for(i=1;i<=sc;i++)
                {
                    System.out.print("*");
                }
                for(j=1;j<=hc;j++)
                {
                 System.out.print("#");
                }
            }
        
            else
            { 
                for(i=1;i<=hc;i++)
                {
                    System.out.print("#");
                }
                for(j=1;j<=sc;j++)
                {
                 System.out.print("*");
                }
            }
             System.out.print("\n");
             if(k<n/2)
             {
            sc++;
            hc--;
             }
             else
            {
            sc--;
            hc++;
             }
                 
             
        }
    }
}