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javaformattingscjp

Use of locale-specific grouping separator in java Formatter

I'm studying for SCJP, and my book (Sierra's) says about the Formatter class that I can use the flag "," to use locale-specific grouping separator. If I understand well, this line of code:

System.out.printf("%2$,f + %1$,f", 123.7, 456.2);

should produce:

456,200000 + 123,700000

with comma, but it's actually producing:

456.200000 + 123.700000

What I'm doing wrong?

Solution 
  •   System.out.printf("%2$,f + %1$,f", 1232.7, 4562343.2);

    will give you 

    4,562,343.200000 + 1,232.700000

    The numbers you are using for your example are less than 1000 and do not need thousand separators.