Can this iterative method be implemented recursively?

public class Main
{
    public static void pyr(int n)
    {      
        for(int i=1;i<=n;i++)
        {
             for(int j = 1;j<=i;j++)
             {  
                  System.out.print("*");
  开发者_如何学JAVA           }
             System.out.println();
        }
    }
 }

Can such a code for a pyramid like shape of asteriks be implemented recursively ? if so especially the 2 loops as the first one is for leveling while the second is used to fill each level.

The answer is yes - basically everything iterative can be done recursively, sometimes it is much easier, but more time consuming.

For your question - this does the trick:

public static void main(String[] args) 
{
    printPyramid(7);
}

public static void printPyramid(int lines)
{
    if (lines > 1)
    {
        printPyramid(lines-1);
    }
    printLine(lines);
    System.out.println("");
}

public static void printLine(int level)
{
    if (level > 0)
    {
        System.out.print("*");
        printLine(level-1);
    }
}

"Any function that can be evaluated by a computer can be expressed in terms of recursive functions without the use of iteration, in continuation-passing style; and conversely any recursive function can be expressed in terms of iteration." Source: http://kevin.vanzonneveld.net/techblog/tag/recursion/

Edit: added source link.

Sure, just have a look at the chapter of the wikipedia article. I've seen a mathematic proof also but I forgot where I can find it.

In your case just use two methods. One prints stars as long as the input parameter is greater 0.

public void static printStar(int n) {
  if(n > 0) {
      System.out.print("*");
      --n;
      printStar(n);
  }
}

This code handles your inner loop.

public void static printPyramid(int n, int start) {
  if(start >= n) {
    return;
  }

  printStar(start);
  ++start;
  printPyramid(n, start);
}

This code handles your outer loop. Where start is your i.