The statement System.out.printf("%3.1f", 1234.56) outputs __.

The statement System.out.printf("%3.1f", 1234.56) will output "1234.6".

Here's the step by step explanation:

1. System.out.printf is a method in Java that is used to print formatted strings. The method takes a format string and a variable number of arguments and prints a string that is formatted accordingly.

2. The format string "%3.1f" tells the method how to format the output. The 'f' indicates that the argument is a floating point number. The '3.1' before the 'f' indicates the minimum width and precision of the output.

3. The '3' is the minimum number of characters that should be printed. If the number is less than 3 characters long, it will be padded with spaces. However, in this case, the number 1234.56 is more than 3 characters long, so this part of the format string has no effect.

4. The '.1' indicates the precision of the output, or the number of digits to be printed after the decimal point. So, the number 1234.56 is rounded to one decimal place, resulting in 1234.6.

5. Therefore, the output of the statement System.out.printf("%3.1f", 1234.56) is "1234.6".