在静态上下文中将弃用的 Java 日期替换为 Calendar.set 或 GregorianCalendar.set

Question

I'm working on Android project using Java and Android Studio IDE is warning me Date(int, int, int) is deprecated as of API16, but when I replace it to Calendar.set the build fails as non-static method cannot be referenced in a static context.

This method is being called on a date picker onItenSelectedListener that is static

How it can be deprecated if there is no replacement that can be really used?

Answer 1

java.time and ThreeTenABP

Use LocalDate from java.time, the modern Java date and time API. It's much nicer to work with.

    int year = 2019;
    int month = 10;
    int day = 15;

    LocalDate date = LocalDate.of(year, month, day);
    System.out.println(date);

The output from this snippet is:

2019-10-15

LocalDate numbers both years and months the same way humans do, so there's no subtracting funny values to adjust. If you need a Date for an API not yet upgraded to java.time, the conversion goes like this:

    Instant startOfDay = date.atStartOfDay(ZoneId.systemDefault()).toInstant();
    Date oldfashionedDate = DateTimeUtils.toDate(startOfDay);
    System.out.println(oldfashionedDate);

Tue Oct 15 00:00:00 CEST 2019

The classes Date , Calendar and GregorianCalendar are all poorly designed and all long outdated. So do consider not using them.

Question: Doesn't java.time require Android API level 26?

java.time works nicely on both older and newer Android devices. It just requires at least Java 6 .

• In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in. Only in this case for converting from Instant to Date use Date.from(startOfDay) .
• In non-Android Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310; see the links at the bottom).
• On (older) Android use the Android edition of ThreeTen Backport. It's called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.

Links

• Oracle tutorial: Date Time explaining how to use java.time.
• Java Specification Request (JSR) 310 , where java.time was first described.
• ThreeTen Backport project , the backport of java.time to Java 6 and 7 (ThreeTen for JSR-310).
• ThreeTenABP , Android edition of ThreeTen Backport
• Question: How to use ThreeTenABP in Android Project , with a very thorough explanation.

Answer 2

I solved the problem replacing

return new Date(year-1900, month, day)

by

GregorianCalendar calendar = new GregorianCalendar(TimeZone.getTimeZone("GMT"));
calendar.set(year, month-1, day);
return calendar.getTime();