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A practical tip every day, number formatting

String.format is usually used for formatting numbers, but note that there is a DecimalFormat for formatting numbers

Today we’re going to do DecimalFormat

1. DecimalFormat Instruction

DecimalFormat is easy to use, mainly with the help of two placeholders, 0 and #. The difference is that when the number of placeholders is more than the actual number, the prefix 0 is used. # doesn’t need to be completed

This might be a little confusing, but here’s an example

double num = 3.1415926;
System.out.println(new DecimalFormat("000", num));
System.out.println(new DecimalFormat("# # #", num));
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The above two outputs are integers only, but the output is different, as follows

003
3
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In simple terms, it is 0, mainly used for fixed-length output, for insufficient, prefix complement 0

Integer # decimal

In addition to the basic posture above, it is more common to set the number of digits of integers and decimals

System.out.println(new DecimalFormat("000.00", num));
System.out.println(new DecimalFormat("# # # # #", num));
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The output is as follows

003.14
3.14
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The percentage

Percentage output is also a common case, and DecimalFormat is easy

System.out.println(new DecimalFormat("000.00", num));
System.out.println(new DecimalFormat("# # # # #", num));
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The output is as follows

314.16%
314.16%
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Scientific count

In non-professional scenarios, science and technology are less likely

System.out.println(new DecimalFormat(000.00 "e0", num));
System.out.println(new DecimalFormat("###.##E0", num));
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The output is as follows

314.16 e-2 3.1416 e0Copy the code

Money style output

The interesting thing about finance-related money output is that it can be easily separated by a comma

double num = 31415926
System.out.println(new DecimalFormat(", # # #", num));
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The output is as follows

31415926Copy the code

Embedded template output

Format templates, in addition to the basic 000, ###, can be placed directly in a String, similar to the effect of string.format

Like showing the balance

double num = 31415926
System.out.println(new DecimalFormat("Your balance,###￥", num));
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The output is as follows

Your balance is ￥31,415,926Copy the code

Series of blog posts:

  • Practical tip 1: String placeholder replacement -JDK version
  • Practice Tip 2: Array and list are rotated
  • Practice Tip 3: String and container transfer
  • Practical tip 4: Elegant string concatenation implementation
  • Practice tip 5: Hump and underline turn each other
  • Practice Tip 6: Special use of enumeration
  • Practice Tip 7: Sort carefully
  • Practice tip 8: Specify the initial size of the container
  • List. SubList is used incorrectly StackOverflowError
  • Practice Tip # 10: Immutable containers

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