Java java.time.format.DateTimeFormatterBuilder用法及代码示例

// Java Program to Illustrate DateTimeFormatterBuilder class
// by invoking appendValue() Method of this class
// Importing required classes from respective packages
import java.io.*;
import java.lang.*;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.TextStyle;
import java.time.temporal.ChronoField;
// Main class
public class GFG {
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an object of this class
        // inside main() method
        DateTimeFormatterBuilder builder
            = new DateTimeFormatterBuilder();
        // Now creating object of DateTimeFormatter class
        // over which appendValue() method is invoked
        DateTimeFormatter formatter
            = builder.appendLiteral("Day is:")
                  .appendValue(ChronoField.DAY_OF_MONTH)
                  .appendLiteral(", Month is:")
                  .appendValue(ChronoField.MONTH_OF_YEAR)
                  .toFormatter();
        // Creating object of LocalDateTime class
        // invoking now() method over it
        LocalDateTime dateTime = LocalDateTime.now();
        // Formatting the date and lately
        // storing it in a string
        String str = dateTime.format(formatter);
        // Print and display the day and month
        System.out.println(str);
    }
}

// Java program to illustrate DateTimeFormatterBuilder
// Using optionalStart() and optionalEnd() Methods
// Importing required libraries
import java.io.*;
import java.lang.*;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.temporal.ChronoField;
// Main class
public class GFG {
    // Main driver methods
    public static void main(String[] args)
    {
        // Creating an object of DateTimeFormatter class
        DateTimeFormatter parser
            = new DateTimeFormatterBuilder()
                  .appendPattern("[yyyy][yyyyMM][yyyyMMdd]")
                  .optionalStart()
                  .parseDefaulting(
                      ChronoField.MONTH_OF_YEAR, 1)
                  .parseDefaulting(ChronoField.DAY_OF_MONTH,
                                   1)
                  .optionalEnd()
                  .toFormatter();
        // Print and display statements
        // Execute if only year is given in parameter
        System.out.println(
            parser.parse("2021", LocalDate::from));
        // Execute if year and month is given
        System.out.println(
            parser.parse("202106", LocalDate::from));
        // Execute if year, month and date is given
        System.out.println(
            parser.parse("20210631", LocalDate::from));
    }
}

// Java Program to illustrate DateTimeFormatterBuilder Class
// Importing required classes
import java.io.*;
import java.lang.*;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.TextStyle;
import java.time.temporal.ChronoField;
import java.util.Locale;
// Main class
// DateTimeFormatterBuilderExample
class GFG {
    // Main driver method
    public static void main(String[] args)
    {
        // Creating object of LocalDate class
        // inside main() method
        LocalDate date = LocalDate.of(2021, 6, 30);
        // Creating object of DateTimeFormatter class
        // Object 1
        DateTimeFormatter formatter
            = DateTimeFormatter.ofPattern("dd/MM/yyyy");
        // Object 2
        DateTimeFormatter italianFormatter
            = DateTimeFormatter.ofPattern("d. MMMM yyyy",
                                          Locale.ITALIAN);
        // Print and display date in format XX-XX-XX
        System.out.println(
            date.format(DateTimeFormatter.ISO_LOCAL_DATE));
        // Print and display date in format XX/XX/XX
        System.out.println(date.format(formatter));
        // Print and display Italian date formatter
        System.out.println(date.format(italianFormatter));
        // Object 3
        DateTimeFormatter complexFormatter
            = new DateTimeFormatterBuilder()
                  .appendText(ChronoField.DAY_OF_MONTH)
                  .appendLiteral(". ")
                  .appendText(ChronoField.MONTH_OF_YEAR)
                  .appendLiteral(" ")
                  .appendText(ChronoField.YEAR)
                  .parseCaseInsensitive()
                  .toFormatter(Locale.US);
        // Print and display US date formatter
        System.out.println(date.format(complexFormatter));
    }
}