Keep two significant digits

I encountered a problem at work today, how to keep two significant digits in double type numbers. Baidu will have a lot of answers, and then I found a relatively simple paragraph and shared it with everyone:

Formatting numbers, such as to 2 decimal places, is the most common. Java provides the DecimalFormat class to help you format numbers the way you need them in the fastest way possible. Below is an example:

 

 

[java] view plaincopyprint?
importjava.text.DecimalFormat;  
　　  
publicclassTestNumberFormat{  
　　  
　　publicstaticvoidmain(String[]args){  
　　　　doublepi=3.1415927; //pi  
　　　　// take an integer  
　　　　System.out.println(newDecimalFormat("0").format(pi));　　　//3  
　　　　// take one integer and two decimals  
　　　　System.out.println(newDecimalFormat("0.00").format(pi));　//3.14  
　　　　//Take two integers and three decimals, and fill in the missing part of the integer with 0.  
　　　　System.out.println(new DecimalFormat("00.000").format(pi));// 03.142  
　　　　// get all integer parts  
　　　　System.out.println(newDecimalFormat("#").format(pi));　　　//3  
　　　　// Count as a percentage and take two decimal places  
　　　　System.out.println(new DecimalFormat("#.##%").format(pi));　//314.16%  
　　  
　　　　longc=299792458; //speed of light  
　　　　//Display in scientific notation and take five decimal places  
　　　　System.out.println(newDecimalFormat("#.#####E0").format(c));　//2.99792E8  
　　　　//display as two-digit integer scientific notation, and take four decimal places  
　　　　System.out.println(newDecimalFormat("00.####E0").format(c));　//29.9792E7  
　　　　// Each three is separated by a comma.  
　　　　System.out.println(newDecimalFormat(",###").format(c));　　　//299,792,458  
　　　　// embed formatting into text  
　　　　System.out.println(newDecimalFormat("The speed of light is per second, ###meters.").format(c));  
　　}  
}

 

 

The DecimalFormat class mainly relies on the # and 0 placeholders to specify the length of the number. 0 means padding with 0 if there are not enough digits, # means pulling the number to this position whenever possible. The above example covers almost all the basic usage.