如何获取当前日期和从当前日期算起的未来30天的日期

问题描述

开发人员，希望您一切都好，我正在尝试将当前日期定为2020年9月16日，然后在此之后想要获得下一个30天的日期。抱歉，我是新来的，所以没有正确的问题。如果您有解决方案，请与我们分享，或者有任何疑问，请与我们联系。预先感谢。

解决方法

我建议您使用modern java.time日期时间API和相应的格式API（软件包java.time.format）来完成此操作。从 Trail: Date Time 了解有关现代日期时间API的更多信息。 java.util日期时间API和SimpleDateFormat已过时且容易出错。

如果您的Android API级别仍不兼容Java8，请选中How to use ThreeTenABP in Android Project和Java 8+ APIs available through desugaring。

使用现代的日期时间API进行以下操作：

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

public class Main {
    public static void main(String[] args) {
        // Define a formatter for your custom pattern
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd/MM/yyyy");

        // I've used the default time-zone of your JVM. As per your requirement,you can
        // change to different time-zone e.g as shown in the commented code
        // LocalDate today = LocalDate.now(ZoneId.of("Europe/London"));
        LocalDate today = LocalDate.now();// Same as LocalDate.now(ZoneId.systemDefault())
        // Print in default pattern i.e. in the pattern returned by LocalDate.toString()
        System.out.println("Today in the default pattern: " + today);
        // Print in the defined custom pattern
        System.out.println("Today in dd/MM/yyyy pattern: " + today.format(formatter));

        // After 30 days from today
        LocalDate after30Days = today.plusDays(30);
        System.out.println("After 30 days: " + after30Days.format(formatter));

        // After 30 days from today
        LocalDate afterOneMonth = today.plusMonths(1);
        System.out.println("After one month: " + afterOneMonth.format(formatter));
    }
}

输出：

Today in the default pattern: 2020-09-16
Today in dd/MM/yyyy pattern: 16/09/2020
After 30 days: 16/10/2020
After one month: 16/10/2020

,

这是使用java.time的方法，现在可以通过Android API Desugaring使用它来降低Android API版本：

public static void main(String[] args) {
    // get the date of today
    LocalDate today = LocalDate.now();
    // get the date that is 30 days later
    LocalDate thirtyDaysInFuture = today.plusDays(30);
    // get the date a month later (not necessarily the same date as 30 days later)
    LocalDate aMonthInFuture = today.plusMonths(1);
    // define a desired format for output (use log(...) in Android instead of System.out)
    DateTimeFormatter customDtf = DateTimeFormatter.ofPattern("dd/MM/uuuu");
    // print the results using the formatter defined above
    System.out.println("Today:\t\t\t" + today.format(customDtf));
    System.out.println("Thirty days later:\t" + thirtyDaysInFuture.format(customDtf));
    System.out.println("One month later:\t" + aMonthInFuture.format(customDtf));
}

输出：

Today:              16/09/2020
Thirty days later:  16/10/2020
One month later:    16/10/2020