在Java Formatter中使用特定于语言环境的分组分隔符

Question

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?

Answer 1

  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.