Java String.format() syntax

Question

I'm trying to print the following output on the screen.

     #
    ##
   ###
  ####
 #####
######

This is my code,

public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int num = Integer.parseInt(sc.nextLine());

        for(int i= 1; i <= num; i++){
            String spc = String.format("%" +  (num - i) + "s", " ");
            String hash = String.format("%" + i + "#", "#");
            System.out.println(spc+hash);
        }
    }

I get the following error,

Exception in thread "main" java.util.FormatFlagsConversionMismatchException: Conversion = s, Flags = #
    at java.util.Formatter$FormatSpecifier.failMismatch(Formatter.java:4298)
    at java.util.Formatter$FormatSpecifier.printString(Formatter.java:2882)
    at java.util.Formatter$FormatSpecifier.print(Formatter.java:2763)
    at java.util.Formatter.format(Formatter.java:2520)
    at java.util.Formatter.format(Formatter.java:2455)
    at java.lang.String.format(String.java:2940)
    at Solution.main(Solution.java:13)

I can understand my String.format has not been done right, but the docs are confusing on printing the character # Any help appreciated.

mmuzahid · Accepted Answer · 2016-02-11 04:28:01Z

3

You could try like this:

for (int i = 1; i <= num; i++) {
    String spc = (i == num) ? "" : String.format("%" + (num - i) + "s", " ");
    String hash = String.format("%" + i + "s", "#").replace(' ', '#');
    System.out.println(spc + hash);
}

Output:

     #
    ##
   ###
  ####
 #####
######

edited Feb 11, 2016 at 4:28

answered Feb 10, 2016 at 5:10

mmuzahid

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2 Comments

Zeus Over a year ago

I'm confused with the documentation, can you explain your answer a bit, and what does % and s mean.

mmuzahid Over a year ago

% is a special character for formatting. s stand for String

user unknown · Accepted Answer · 2016-02-10 04:28:53Z

2

I guess you wanted to write:

       String hash = String.format("%" + i + "s", "#");

Reading the error message helped me in finding this error, though you didn't marked where line 13 is.

answered Feb 10, 2016 at 4:28

user unknown

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2 Comments

Zeus Over a year ago

This prints, num-1 spaces with a trailing # 6 times.

user unknown Over a year ago

Yes, I didn't want to solve your problem, but point out, where you're stuck.

Mohith P · Accepted Answer · 2016-02-10 04:58:15Z

0

Try this

for(int i= 1; i <= num; i++)
        {
            if((num-i)>0)
            {
                String spc = String.format("%" +  (num - i) + "S", " ");
                String hash = String.format("%" + i + "s", "#");
                System.out.println(spc+hash);
            }
        }

answered Feb 10, 2016 at 4:58

Mohith P

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1 Comment

mmuzahid Over a year ago

I think it produce Wrong output.

Ganesh · Accepted Answer · 2018-03-31 08:49:45Z

0

I came across the same output. Here is one solution. Just in case someone stumbles again.

Instead of creating # and spaces separately, We can define width to the format method. Refer Java String Format Examples

String hash = "";
for (int i = 1; i <=n; i++) {
     hash+="#";
     System.out.println(String.format("%"+n+"s",hash));
}

answered Mar 31, 2018 at 8:49

Ganesh

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