1. DateFormat abstract class
DateFormat is an abstract time formatting class. Formatting is a string that becomes a specified format.
DateFormat is an abstract class of date/time formatting. It formats and parses date or time in a language-independent manner.
DateFormat can help format and parse dates in any locale. For months, weeks, and even calendar formats (lunar and solar calendars), the codes can be completely independent of the locale conventions.
1.1. SimpleDateFormat类
In the process of formatting and parsing date and time, its subclass SimpleDateFormat is more commonly used.
The SimpleDateFormat class is a concrete class for formatting and parsing dates in a language environment-related way.
It provides methods for formatting date and time (date time string) and parsing date and time (string date time).
1.2. SimpleDateFormat class date and time mode
1.3. SimpleDateFormat construction method
SimpleDateFormat()。
SimpleDateFormat(String pattern) is created according to the specified pattern.
SimpleDateFormat object.
1.4. SimpleDateFormat() common methods
String format(Date date); Format a java.util.Date object as a date according to the specified mode.
Date parse(String date); Parse a date string into a java.util.Date type object according to the specified pattern.
1.5. Program example
Convert the date into a string according to the specified pattern and print it
Convert string to date
2. NumberFormat class
NumberFormat is an abstract class for number formatting, which provides methods for formatting and parsing values.
2.1. NumberFormat common methods
String format (double d) format the number as a string
Number parse(String s) parses the string into numbers
void setMaximumFractionDigits(int newValue) Set the maximum decimal places
void setMinimumFractionDigits(int newValue) Set minimum decimal places
Under normal circumstances, its subclass DecimalFormat is used to format or parse numbers.
2.2. DecimalFormat子类
DecimalFormat is a specific subclass of NumberFormat, used to format decimal numbers. This class is designed with various functions that enable it to parse and format numbers in any language environment, including support for Western, Arabic, and Hindi numbers.
2.3. DecimalFormat construction method
DecimalFormat()
DecimalFormat(String pattern) constructs the object according to the specified pattern
2.4. DecimalFormat number pattern character
2.5. Commonly used construction methods of DecimalFormat class
String format(double d); format numbers as strings
Number parse(String str); parse string numbers into Number objects
2.6. Program example
Convert the data into a string according to the specified mode and print it out
1. By comparing the two data, we can know that the format method will start from the decimal point to the left according to the specified pattern.
Parse the string according to the specified pattern
