Formatting output numbers in Java

Formatting output numbers in Java

In actual work, you often need to set the output format of numbers, such as output in percentages or decimal places. The following is a summary.
Main classes used: Java. Text. decimalformat
1. The following two methods can be used to instantiate an object:
Decimalformat df = (decimalformat) numberformat. getinstance ();
Decimalformat DF1 = (decimalformat) decimalformat. getinstance ();
Because decimalformat inherits from numberformat.
2. Set the number of decimal places
The default number of decimal places is 3, for example:
Decimalformat df = (decimalformat) numberformat. getinstance ();
System. Out. println (DF. Format (12.3456789 ));
Output: 12.346
Now we can set the decimal point to two places using the following method:
DF. setmaximumfractiondigits (2 );
System. Out. println (DF. Format (12.3456789 ));
The output is: 12.35.
3. To convert a number to a percentage, you can use either of the following methods:
(1)
DF. applypattern ("##. ##% ");
System. Out. println (DF. Format (12.3456789 ));
System. Out. println (DF. Format (1 ));
System. Out. println (DF. Format (0.015 ));
Output: 1234.57% 100% 1.5%
(2)
DF. setmaximumfractiondigits (2 );
System. Out. println (DF. Format (12.3456789*100) + "% ");
System. Out. println (DF. Format (1*100) + "% ");
System. Out. println (DF. Format (0.015*100) + "% ");
The output is as follows:
1,234.57% 100% 1.5%
4. Set Group Size
Decimalformat DF1 = (decimalformat) decimalformat. getinstance ();
Df1.setgroupingsize (2 );
System. Out. println (df1.format (123456789 ));
Output:, 89
You can also disable group settings by using df1.setgroupingused (false);, for example:
Decimalformat DF1 = (decimalformat) decimalformat. getinstance ();
Df1.setgroupingsize (2 );
Df1.setgroupingused (false );
System. Out. println (df1.format (123456789 ));
Output: 123456789
5. Set decimal to 2 digits
Decimalformat df2 = (decimalformat) decimalformat. getinstance ();
Df2.applypattern ("0.00 ");
System. Out. println (df2.format (1.2 ));
Output: 1.20