Question

I am studying the Pyramid Numbers in Java which has a code like this.

public class PyramidCharForLup {

  public static void main(String[] args) {

     int x = 7;  
     for (int i = 1; i <= x; i++) 
     {  
         for (int j = 1; j <= x - i; j++)  
             System.out.print("   ");  
         for (int k = i; k >= 1; k--)  
             System.out.print((k >=10) ?+ k : "  " + k);  
         for (int k = 2; k <=i; k++)  
             System.out.print((k>= 10) ?+ k : "  " + k);  
         System.out.println();  
     }  
   }
 }

The output is

                    1
                 2  1  2
              3  2  1  2  3
           4  3  2  1  2  3  4
        5  4  3  2  1  2  3  4  5
     6  5  4  3  2  1  2  3  4  5  6
  7  6  5  4  3  2  1  2  3  4  5  6  7

---

I chop the code and study it line by line I’m already studying in this line so far.. heheh

So here’s the code that I want to ask.

public class PyramidCharForLup {

   public static void main(String[] args) 
   {
      int x = 7;
      for (int i = 1; i <= x; i++) {
         for (int j = 1; j <= x - i; j++)
            System.out.print(j);

      }
   }
}

the output of this is 123456123451234123121 for clarification if you are to arrange
123456 12345 1234 123 12 1

First Question: is i in the code for (int j = 1; j <= x - i; j++) become i= 1234567?
Second Question: from the initialization which is one if increment 1..2..3..5..6..7.. are the increment subtracting the last number from 1234567 like

1234567-1… 123456 – 1 … 12345 – 1 … 1234 – 1 … 123 – 1 … 12-1…1-0…. till false Am I right?

and that’s the reason why i got this output 123456 12345 1234 123 12 1

Answer 1

Your code has two nested loops (one loop runs inside the other). This is what happens:

1. You set x to 7
2. You are starting the outer loop, setting i = 1. Since 1 <= 7 the loop is entered.
3. You are starting the inner loop, setting j = 1. Since 1 <= 6 (7-1 from x – i) the loop is entered.
4. j (1) is printed.
5. j is increased with 1 and since 2 is less than 6 the inner loop continues.
6. j (2) is printed.

This goes on until j is 6.

1. j (6) is printed.
2. j is increase by 1 and is now 7 which is not <= 6, so the inner loop exits.
3. i is increased by one (and is now 2).
4. The inner loop is entered again, setting j to 1. Since j < 5 (7-2 from x – i) the loop is entered.
   11 j (1) is printed.
   12 j is increase by one and is now 2. Since 2 < 6 the loop continues.

This goes on until i reaches 7. When i the is increased by 1 it is 8 which is not <= 7 so the outer loop also exists and your program is done.

Your program will count and write the digits from 1..6, then from 1..5 until it reaches 1..1