Format a number

We often need to format numbers, such as taking 2 decimal places, which is the most common. Java provides the decimalformat class to help you format numbers as quickly as possible. The following is an example: Import Java. text. decimalformat; public class testnumberformat {public static void main (string [] ARGs) {double Pi = 3.1415927; // The circumference rate // gets an integer system. out. println (New decimalformat ("0 "). format (PI); // 3 // take an integer and two decimal places system. out. println (New decimalformat ("0.00 "). format (PI); // 3.14 // take two integers and three decimal places. The less integer is filled with 0. System. out. println (New decimalformat ("00.000 "). format (PI); // 03.142 // obtain all integer parts of the system. out. println (New decimalformat ("#"). format (PI); // 3 // count by percentage, and take two decimal places system. out. println (New decimalformat ("#. # % "). format (PI); // 314.16% long c = 299792458; // speed of light // display as a scientific notation, and take the five decimal places system. out. println (New decimalformat ("#. ##### E0 "). format (c); // 2.99792e8 // displays the scientific notation of two integers, and takes four decimal places. out. println (New decimalformat ("00. #### E0 "). format (c); // 29.9792e7 // each three digits are separated by commas. out. println (New decimalformat (",###"). format (c); // 299,792,458 // embed the format into the text system. out. println (New decimalformat ("the speed of light is every second, ### meters. "). Format (c) ;}} running result: 33.1403.1423314.16% 2.99792e829.9792e7299, 792,458 light speed is 299,792,458 meters per second. The decimalformat class mainly uses the # And 0 placeholder numbers to specify the number length. 0 indicates that if the number of digits is insufficient, it is filled with 0. # indicates that the number is pulled to this position whenever possible. The above example contains almost all basic usage