Java IO.pdf - Nguyen Dang Binh

public class MinimumWage {
public static void main(String[] args) {
NumberFormat dollarFormat =
NumberFormat.getCurrencyInstance(Locale.ENGLISH);
double minimumWage = 5.15;
System.out.println("The minimum wage is "
+ dollarFormat.format(minimumWage));
System.out.println("A worker earning minimum wage and working for
forty");
System.out.println("hours a week, 52 weeks a year, would earn "
+ dollarFormat.format(40*52*minimumWage));
}
}
This program prints:
The minimum wage is $5.15
A worker earning minimum wage and working for forty
hours a week, 52 weeks a year, would earn $10,712.00
Java I/O
Notice how nicely the numbers are formatted. Nowhere did I add dollar signs, say that I
wanted exactly two numbers after the decimal point, or say that I wanted to separate the
thousands with commas. The NumberFormat class took care of that.
There are limits to how far currency formatting goes. Currency formats may change the
currency sign in different locales, but they won't convert the values (between U.S. and
Canadian dollars or between U.S. dollars and British pounds, for example). Since conversion
rates float from day to day and minute to minute, that's a bit much to ask of a static class. If
you want to do this, you need to provide some source of the conversion rate information,
either from user input or pulled off the network.
16.3.5 Percent Formats
Number formats can also handle percentages in a variety of international formats. In grammar
school math you learned that a number followed by a percent sign is really one-hundredth of
its apparent value. Thus, 50% is really decimal 0.5, 100% is 1.0, 10% is 0.1, and so on.
Percent formats allow you to use the actual decimal values in your code but print out the
hundred-times larger percent values in the output. You request the default locale's percentage
formatter with the static method NumberFormat.getPercentInstance():
public static final NumberFormat getPercentInstance()
To get a percentage formatter for a different locale, pass the locale to
NumberFormat.getPercentInstance():
public static NumberFormat getPercentInstance(Locale inLocale)
Example 16.5 prints a table of percents between 1% and 100%. Notice that doubles are used
in the code, but integral percents appear in the output.
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