IllegalFormatFlagsException: Using invalid padding specifier for integers

[Last Updated: Nov 8, 2025]

Class:

java.util.IllegalFormatFlagsException

Cause of the exception

This error can occur when we try to use negative sign with zero padding specifier %0Nd where N can be any integer.

package com.logicbig.example.illegalformatflagsexception;

public class IllegalFormatFlagsExceptionRightZeroPadding {
    public static void main(String[] args) {
        //right zero padding for integers not possible
        System.out.printf("%0-5d", 21);
    }
}

Output

java.util.IllegalFormatFlagsException: Flags = '-0'
    at java.util.Formatter$FormatSpecifier.checkNumeric (Formatter.java:3181)
    at java.util.Formatter$FormatSpecifier.checkInteger (Formatter.java:3136)
    at java.util.Formatter$FormatSpecifier.<init> (Formatter.java:2874)
    at java.util.Formatter.parse (Formatter.java:2713)
    at java.util.Formatter.format (Formatter.java:2655)
    at java.io.PrintStream.format (PrintStream.java:1209)
    at java.io.PrintStream.printf (PrintStream.java:1105)
    at com.logicbig.example.illegalformatflagsexception.IllegalFormatFlagsExceptionRightZeroPadding.main (IllegalFormatFlagsExceptionRightZeroPadding.java:13)
    at java.lang.Thread.run (Thread.java:832)

Avoiding the exception

Avoid using negative sign for integer zero padding

package com.logicbig.example.illegalformatflagsexception;

public class IllegalFormatFlagsExceptionRightZeroPaddingFix {

    public static void main(String[] args) {
        //right zero padding for integers not possible
        System.out.printf("%05d", 21);
    }
}

IllegalFormatFlagsException: Using invalid padding specifier for integers

Class:

Cause of the exception

Output

Avoiding the exception

Output

See Also