A FormatFlagsConversionMismatchException is a runtime exception in Java that occurs when there is an incompatibility between a format flag and a conversion in string formatting, often encountered during the use of methods like String.format() and printf(). This exception is part of the hierarchy that extends from IllegalFormatException and is triggered when specific flags, like the # flag, are incorrectly used with incompatible format specifiers such as %s. Examples illustrate common scenarios, such as forgetting to escape the % character in printf() statements, leading to this exception. To handle such exceptions, developers are advised to use try-catch blocks, ensure compatibility between flags and conversions, and precisely follow the syntax for string formatting while considering alternatives like StringBuilder. Tools like Rollbar can assist in managing and tracking such errors in real time, providing a more confident approach to deploying production code.