Lära Parsing Dates with LocalDate.parse() | Parsing Dates and Formatting Tables

Understanding how to work with dates is essential in Java, especially when you need to convert string representations of dates into objects that your program can manipulate. The LocalDate class, introduced in Java 8, provides a robust way to represent dates without time or timezone information. Parsing dates from strings is a common task, such as when reading input from users, files, or network sources. Using LocalDate.parse() allows you to transform a properly formatted string into a LocalDate object, enabling safe and reliable date calculations and comparisons.

Main.java


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package com.example;

import java.time.LocalDate;

public class Main {
    public static void main(String[] args) {
        String dateString = "2023-12-31";
        LocalDate date = LocalDate.parse(dateString);
        System.out.println("Parsed date: " + date);
    }
}

The example above uses the default ISO-8601 format (yyyy-MM-dd) that LocalDate.parse() expects. However, real-world data often comes in different formats. To handle this, Java provides the DateTimeFormatter class, which lets you define custom patterns for parsing and formatting dates. By supplying a DateTimeFormatter with the desired pattern to LocalDate.parse(), you can correctly interpret date strings like "31/12/2023" or "12-31-2023".

Main.java


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package com.example;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class Main {
    public static void main(String[] args) {
        String dateString = "31/12/2023";
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd/MM/yyyy");
        LocalDate date = LocalDate.parse(dateString, formatter);
        System.out.println("Parsed date with custom pattern: " + date);
    }
}

1. What happens if the date string does not match the expected pattern in LocalDate.parse()?

2. Which class is used to define custom date patterns for parsing?

3. Fill in the blank: To parse "31-12-2023" as a LocalDate, use the pattern ______.

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 3. Kapitel 1

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Main.java


              123456789101112
            
package com.example;

import java.time.LocalDate;

public class Main {
    public static void main(String[] args) {
        String dateString = "2023-12-31";
        LocalDate date = LocalDate.parse(dateString);
        System.out.println("Parsed date: " + date);
    }
}

Main.java


              1234567891011121314
            
package com.example;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class Main {
    public static void main(String[] args) {
        String dateString = "31/12/2023";
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd/MM/yyyy");
        LocalDate date = LocalDate.parse(dateString, formatter);
        System.out.println("Parsed date with custom pattern: " + date);
    }
}

1. What happens if the date string does not match the expected pattern in LocalDate.parse()?

2. Which class is used to define custom date patterns for parsing?

3. Fill in the blank: To parse "31-12-2023" as a LocalDate, use the pattern ______.

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 3. Kapitel 1