Java 日期格式化風格展示

程式碼範例

import java.util.*;
import java.text.*;

public class StyleDemo {
    public static void main(String[] args) {
        Date now = new Date();
        DateFormat df = DateFormat.getDateInstance();
        DateFormat df1 = DateFormat.getDateInstance(DateFormat.SHORT);
        DateFormat df2 = DateFormat.getDateInstance(DateFormat.MEDIUM);
        DateFormat df3 = DateFormat.getDateInstance(DateFormat.LONG);
        DateFormat df4 = DateFormat.getDateInstance(DateFormat.FULL);

        System.out.println("(Default) Today is " + df.format(now));
        System.out.println("(SHORT)   Today is " + df1.format(now));
        System.out.println("(MEDIUM)  Today is " + df2.format(now));
        System.out.println("(LONG)    Today is " + df3.format(now));
        System.out.println("(FULL)    Today is " + df4.format(now));
    }
}

執行結果（預設 Locale）

(Default) Today is Nov 8, 2000
(SHORT)   Today is 11/8/00
(MEDIUM)  Today is Nov 8, 2000
(LONG)    Today is November 8, 2000
(FULL)    Today is Wednesday, November 8, 2000

四種預定義風格

進階：自訂格式

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
System.out.println(sdf.format(new Date())); // 2024-01-15 14:30:45

注意：SimpleDateFormat 非執行緒安全，多執行緒環境請使用 ThreadLocal 或 Java 8 DateTimeFormatter。