Java Gold Countermeasures: Format

Introduction

This article summarizes the format as a summary of Java Gold learning.

What is a format?

Data handled by Java is displayed according to the display location. For formatting when you want to change the format.

Format by number, date, etc. Because the method is different, the format is below Summarize the method.

List of main classes used in numeric format

java.text.NumberFormat java.text.DecimalFormat

■ java.text.NumberFormat

NumberFormat cannot be new, so Get the object by static method.

The main methods of NumberFormat are as follows

** ▼ Usage example **

java.text.NumberFormat

//Output result: 1,000
NumberFormat format = NumberFormat.getInstance();
System.out.println(format.format(1000));

//Output result: ¥ 1,000
NumberFormat format = NumberFormat.getCurrencyInstance();
System.out.println(format.format(1000));

//Output result: 1000
try {
	NumberFormat format = NumberFormat.getInstance(Locale.JAPAN);
	String numberStr    = "1000";
	Number value1       = format.parse(numberStr);
	System.out.println(value1);
} catch (ParseException e) {
	//A value different from the specified locale (numberStr= "$1000") Is specified
}

■ java.text.DecimalFormat

DecimalFormat, unlike NumberFormat, gets an object with new. In addition, it can be freely formatted by using the following patterns.

** ▼ Usage example **

//Output: 1,11111
DecimalFormat formatter = new DecimalFormat("#,#####");
System.out.println(formatter.format(111111));

//Output: 01,1111
DecimalFormat formatter = new DecimalFormat("00,0000");
System.out.println(formatter.format(11111));

//Output: ¥ 11,11,11
DecimalFormat formatter = new DecimalFormat("\u00a5##,##");
System.out.println(formatter.format(111111));

//Remarks (filled with 0)
//DecimalFormat type
//Output: 0100.00
DecimalFormat formatter = new DecimalFormat("####.##");
formatter.setMinimumFractionDigits(2);
formatter.setMaximumFractionDigits(4);
formatter.setMinimumIntegerDigits(4);
formatter.setMaximumIntegerDigits(6);
System.out.println(formatter.format(100));

List of main classes used in date format

java.time.format.DateTimeFormatter

■ DateTimeFormatter

List of mainly used methods

Pattern string list

LocalDate date = LocalDate.of(2020, Month.JULY, 6);
LocalTime time = LocalTime.of(10, 20, 30);
LocalDateTime dateTime = LocalDateTime.of(date, time);

//Output result below
// 2020/07/06
// 2020/07/06
DateTimeFormatter formatter1 = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM);
System.out.println(formatter1.format(date));
System.out.println(formatter1.format(dateTime));

// 10:20:30
//UnsupportedTemporalTypeException when formatting date
DateTimeFormatter formatter2 = DateTimeFormatter.ofLocalizedTime(FormatStyle.MEDIUM);
System.out.println(formatter2.format(time));

// 10:20
DateTimeFormatter formatter3 = DateTimeFormatter.ofPattern("hh:mm");
System.out.println(formatter3.format(time));

• Refer to here for FormatStyle.