%d means number. %0nd means zero-padded number with a length. You build n by subtraction in your example. %s is a string. Your format string ends up being this: "%03d%s", 0, "Apple"
printf("%. 2f", value); The %. 2f syntax tells Java to return your variable (value) with 2 decimal places (.
The most common way of formatting a string in java is using String. format(). If there were a “java sprintf” then this would be it.
In your example, it is a placeholder character. It means when % is encountered, the next character determines how to interpret the argument and insert it into the printed result. %s means interpret as string, %d is for digit, %x is digit in hexadecimal, %f is for float, etc....
From this thread, there are different ways to do this:
double r = 5.1234;
System.out.println(r); // r is 5.1234
int decimalPlaces = 2;
BigDecimal bd = new BigDecimal(r);
// setScale is immutable
bd = bd.setScale(decimalPlaces, BigDecimal.ROUND_HALF_UP);
r = bd.doubleValue();
System.out.println(r); // r is 5.12
f = (float) (Math.round(n*100.0f)/100.0f);
DecimalFormat df2 = new DecimalFormat( "#,###,###,##0.00" );
double dd = 100.2397;
double dd2dec = new Double(df2.format(dd)).doubleValue();
// The value of dd2dec will be 100.24
The DecimalFormat() seems to be the most dynamic way to do it, and it is also very easy to understand when reading others code.
You and String.format()
will be new best friends!
https://docs.oracle.com/javase/1.5.0/docs/api/java/util/Formatter.html#syntax
String.format("%.2f", (double)value);
Be aware that classes that descend from NumberFormat (and most other Format descendants) are not synchronized. It is a common (but dangerous) practice to create format objects and store them in static variables in a util class. In practice, it will pretty much always work until it starts experiencing significant load.
Round numbers, yes. This is the main example source.
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import java.util.*;
import java.text.*;
public class DecimalFormatDemo {
static public void customFormat(String pattern, double value ) {
DecimalFormat myFormatter = new DecimalFormat(pattern);
String output = myFormatter.format(value);
System.out.println(value + " " + pattern + " " + output);
}
static public void localizedFormat(String pattern, double value, Locale loc ) {
NumberFormat nf = NumberFormat.getNumberInstance(loc);
DecimalFormat df = (DecimalFormat)nf;
df.applyPattern(pattern);
String output = df.format(value);
System.out.println(pattern + " " + output + " " + loc.toString());
}
static public void main(String[] args) {
customFormat("###,###.###", 123456.789);
customFormat("###.##", 123456.789);
customFormat("000000.000", 123.78);
customFormat("$###,###.###", 12345.67);
customFormat("\u00a5###,###.###", 12345.67);
Locale currentLocale = new Locale("en", "US");
DecimalFormatSymbols unusualSymbols = new DecimalFormatSymbols(currentLocale);
unusualSymbols.setDecimalSeparator('|');
unusualSymbols.setGroupingSeparator('^');
String strange = "#,##0.###";
DecimalFormat weirdFormatter = new DecimalFormat(strange, unusualSymbols);
weirdFormatter.setGroupingSize(4);
String bizarre = weirdFormatter.format(12345.678);
System.out.println(bizarre);
Locale[] locales = {
new Locale("en", "US"),
new Locale("de", "DE"),
new Locale("fr", "FR")
};
for (int i = 0; i < locales.length; i++) {
localizedFormat("###,###.###", 123456.789, locales[i]);
}
}
}
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