The formatting can be customized by specifying the format string in the java.util.logging.SimpleFormatter.format property. The given LogRecord will be formatted as if by calling:

    String.format(format, date, source, logger, level, message, thrown);
 

1. format - the java.util.Formatter format string specified in the java.util.logging.SimpleFormatter.format property or the default format.
2. date - a ZonedDateTime object representing event time of the log record in the ZoneId.systemDefault() system time zone.
3. source - a string representing the caller, if available; otherwise, the logger's name.
4. logger - the logger's name.
5. level - the log level.
6. message - the formatted log message returned from the Formatter.formatMessage(LogRecord) method. It uses java.text formatting and does not use the java.util.Formatter format argument.
7. thrown - a string representing the throwable associated with the log record and its backtrace beginning with a newline character, if any; otherwise, an empty string.

Some example formats:

• java.util.logging.SimpleFormatter.format="%4$s: %5$s [%1$tc]%n"

  This prints 1 line with the log level (4$), the log message (5$) and the timestamp (1$) in a square bracket.

       WARNING: warning message [Tue Mar 22 13:11:31 PDT 2011]
       

• java.util.logging.SimpleFormatter.format="%1$tc %2$s%n%4$s: %5$s%6$s%n"

  This prints 2 lines where the first line includes the timestamp (1$) and the source (2$); the second line includes the log level (4$) and the log message (5$) followed by the throwable and its backtrace (6$), if any:

       Tue Mar 22 13:11:31 PDT 2011 MyClass fatal
       SEVERE: several message with an exception
       java.lang.IllegalArgumentException: invalid argument
               at MyClass.mash(MyClass.java:9)
               at MyClass.crunch(MyClass.java:6)
               at MyClass.main(MyClass.java:3)
       

• java.util.logging.SimpleFormatter.format="%1$tb %1$td, %1$tY %1$tl:%1$tM:%1$tS %1$Tp %2$s%n%4$s: %5$s%n"

  This prints 2 lines similar to the example above with a different date/time formatting and does not print the throwable and its backtrace:

       Mar 22, 2011 1:11:31 PM MyClass fatal
       SEVERE: several message with an exception
       

• java.util.logging.SimpleFormatter.format="%1$tb %1$td, %1$tY %1$tl:%1$tM:%1$tS.%1$tN %1$Tp %2$s%n%4$s: %5$s%6$s%n"

  Since JDK 9, java.util.logging uses java.time to create more precise time stamps. The format above can be used to add a .%1$tN to the date/time formatting so that nanoseconds will also be printed:

       Feb 06, 2015 5:33:10.279216000 PM example.Main main
       INFO: This is a test
       

This method can also be overridden in a subclass. It is recommended to use the Formatter.formatMessage(java.util.logging.LogRecord) convenience method to localize and format the message field.