String.format() method of formatting strings, the meaning and usage of different placeholders

learning target:

目标如下：

• String.format() method of formatting strings, the meaning and usage of different placeholders

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Learning Content:

内容：

1. placeholder type
   

2. The String.format() method is a method of formatting strings

3. String: A placeholder "%s" representing the string itself to be output. (Define data type as string)

4. Integer: There is only one placeholder "%d", which represents the integer to be output. (Define data type as int)

5. Floating point number: There is only one placeholder "%.2f", which represents the floating point number to be output, where ".2" represents the number of decimal places to be output, that is, 2 decimal places are retained. (Define the data type as double)

6. Date: The placeholder "%tF" represents the date to be output. "%tF" means that the output date format is "year-month-day", so the format string is "%tF" and the parameter list is date. (Define the data type as Date)

7. Time: The placeholder "%tT" represents the time to be output. "%tT" indicates that the output time format is "hour:minute:second". The parameter list is date. (Define the data type as Date)

8. Bandwidth rate: A placeholder "%.2f" and a text "Mbps" that together represent the bandwidth rate to be output. (Define the data type as double)

9. Currency amount: a placeholder " %.2f ", which represents the currency amount to be output, where ""Indicates the currency symbol, ".2" indicates the number of decimal places to be output, that is, retaining 2 decimal places. Therefore, the format string is "$%.2f" and the parameter list is amount. (The defined data type is double)

10. "%e" outputs a floating point number in scientific notation

11. Use "%o" to output an integer represented in octal notation

12. "%x" outputs an integer represented in hexadecimal, etc.

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