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Why Java double print format is different based on String.format use or not

This code:

 System.out.println(String.format("%f", Math.PI));
 System.out.println(Math.PI);

produces this result on my computer:

3,141593
3.141592653589793

Why does the first line print a semicolon number while the second uses a period?

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4 answers


String.format(String, Object...)

uses formatting rules from Locale.getDefault()

. String.valueOf(double)

no. Use String.format(Locale, String, Object...)

to explicitly specify the language to use.



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The former respect your language setting (which appears to use a comma for the thousands separator).



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The first uses the default locale .

second is probably using a standard (non-localizable) implementation.

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String.format () uses the locale of your system. There should also be a variant of this method, you can pass a specific instance of Locale. When using println () on the other hand, the toString () method is called - in your case Double # toString (), which is more often than not a fairly basic implementation, good enough to represent a clear display of the object.

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