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Javaで時間のない日付を取得するにはどうすればいいですか? 質問する

tag-icon • tag-icon java date
Javaで時間のない日付を取得するにはどうすればいいですか? 質問する

Stack Overflow の質問「タイムスタンプなしで現在の日付を取得する Java プログラム」の続き:

時刻なしで Date オブジェクトを取得する最も効率的な方法は何ですか? これら 2 つの方法以外に方法はありますか?

// Method 1
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date dateWithoutTime = sdf.parse(sdf.format(new Date()));

// Method 2
Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
dateWithoutTime = cal.getTime();

Update:

  1. I knew about Joda-Time; I am just trying to avoid additional library for such a simple (I think) task. But based on the answers so far Joda-Time seems extremely popular, so I might consider it.

  2. By efficient, I mean I want to avoid temporary object String creation as used by method 1, meanwhile method 2 seems like a hack instead of a solution.

ベストアンサー1

Do you absolutely have to use java.util.Date? I would thoroughly recommend that you use Joda Time or the java.time package from Java 8 instead. In particular, while Date and Calendar always represent a particular instant in time, with no such concept as "just a date", Joda Time does have a type representing this (LocalDate). Your code will be much clearer if you're able to use types which represent what you're actually trying to do.

There are many, many other reasons to use Joda Time or java.time instead of the built-in java.util types - they're generally far better APIs. You can always convert to/from a java.util.Date at the boundaries of your own code if you need to, e.g. for database interaction.

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