java循环的小帮助

Question

Hi I am doing some practice problems and trying to print a diagonal line like the example below. I have writen the program you see below and I honestly dont understand what I am doing wrong. I ma java beginner and I cant see how to find the error.

Example:

*
  *
    *
      *
        *

code:

class Diagonal{
  public static void main(String args[]) {
    int row, col;


    for(row = 1; row < 6; row++) {
      for(col = 1; col <= row; col++) {
          if(col==row){
            System.out.print("*");
          } else{
              System.out.print("");
          }
          System.out.println();     
      }
    }
  }
}

I am trying to learn for loops because they really confuse me. Another practice is to print a similar diagonal line but this time from right to left. I cant do that without getting this right however :( I believe they will be pretty similar? Above my reasining is this: As long as the column # is the same as the row number the print the line or otherwise leave a blank....what's wrong with how i did it?

THANK YOU!

Answer 1

You never print any space character. You print an empty String. Replace

System.out.print("");

with

System.out.print(" ");

Also, you write a newline after each column rather than writing one after each row.

Answer 2

String spaces = "";

for(int row = 1; row < 6; row++) {
    System.out.println(spaces+"*");
    spaces += " ";
}

Answer 3

1. Print new lines when entering a star: System.out.println("*");
2. Add spaces: System.out.println(" ");
3. remove the line where you print new lines between columns.

Answer 4

as said before replace black with space and move the end line to the end of the FIRST for() like this:

class Diagonal{
  public static void main(String args[]) {
    int row, col;


    for(row = 1; row < 6; row++) {
      for(col = 1; col <= row; col++) {
          if(col==row){
            System.out.print("*");
          } else{
              System.out.print(" ");
          }
      }
      System.out.println();     
    }
  }
}