Data
Working with data types
The NumberFormat class
The NumberFormat class
java.text.NumberFormat
Three static methods of the NumberFormat class
| Method | Returns a NumberFormat object that has the |
|---|---|
| getCurrencyInstance() | Default currency format ($99,999.99). |
| getPercentInstance() | Default percent format (99%). |
| getNumberInstance() | Default number format (99,999.999). |
Three methods of a NumberFormat object
| Method | Description |
|---|---|
| format(anyNumberType) | Returns a String object that has the format specified by the NumberFormat object. |
| setMinimumFractionDigits(int) | Sets the minimum number of decimal places. |
| setMaximumFractionDigits(int) | Sets the maximum number of decimal places. |
Two NumberFormat methods that are coded in one statement
String majorityString = NumberFormat. getPercentInstance().format(majority);
How to use the NumberFormat class
- You can use one of the static methods to create a NumberFormat object. Then, you can use the methods of that object to format one or more numbers.
- When you use the format method, the result is automatically rounded by using a rounding technique called half-even: The number is rounded up if the preceding digit is odd, but the extra decimal places are truncated if the preceding digit is even.
- The NumberFormat class is in the java.text package, so you'll want to include an import statement when you use this class.
The currency format
double price = 11.575;The percent format
NumberFormat currency = NumberFormat.getCurrencyInstance();
String priceString = currency.format(price); // returns $11.58
double majority = .505;
NumberFormat percent = NumberFormat.getPercentInstance();
String majorityString = percent.format(majority); // returns 50%
The number format with one decimal place
double miles = 15341.253;
NumberFormat number = NumberFormat.getNumberInstance();
number.setMaximumFractionDigits(1);
String milesString = number.format(miles); // returns 15,341.3