Dec 14

When you need to format a number as a percent you can use the ‘%’ symbol in your DecimalFormat string. The static helper method getPercentInstance() can also be used if you don’t need complete control over the format string.

When the % symbol is used the value is first multiplied by 100 before applying the format string. So 0.123 would become 12.3%.

NumberFormat format1 = new DecimalFormat("##.####%");
NumberFormat format2 = NumberFormat.getPercentInstance();

String formatted1 = format1.format(value);
String formatted2 = format2.format(value);

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Feb 25

You can use the setScale() method to control the rounding of a decimal value as shown in the following example:

double value = 123.456789;
BigDecimal bd = new BigDecimal(value).setScale(2, BigDecimal.ROUND_HALF_UP);

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Nov 15

The BigDecimal constructors do not take the Locale into account when parsing number strings.
This means the following code will throw a NumberFormatException

Locale.setDefault(new Locale("nl", "NL"));
String s =  "2.343.298,09324798";
BigDecimal bd = new BigDecimal(s);

To parse localized strings as BigDecimal we instead need to use the DecimalFormat class

		Locale.setDefault(new Locale("nl", "NL"));
		String s =  "2.343.298,09324798";
		DecimalFormat df = (DecimalFormat) NumberFormat.getInstance();
		BigDecimal bd = (BigDecimal) df.parse(s);

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