JAVA | 31

SimpleDateFormat 类实现 String 与 Date 之间的转换。

如果是要实现日期的计算，Calendar 类比 Date 类更合适。

import java.text.SimpleDateFormat;import java.util.Calendar;import java.util.Date;public class Main {    public static void main(String[] args) {        long time = System.currentTimeMillis();        System.out.println(time);        Date date = new Date(time); // long 转换位 Date        System.out.println(date);        System.out.println(date.getTime()); // Date 转换为 long        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");        String str = simpleDateFormat.format(date); // Date 转换为 String        System.out.println(str);        String str1 = "2011-11-11 11:11:11.111";        try {            date = simpleDateFormat.parse(str1); // String 转换为 Date        }catch (Exception e){            e.printStackTrace();        }        System.out.println(date);        Calendar calendar =Calendar.getInstance(); // 取得本类对象        StringBuffer stringBuffer = new StringBuffer();        stringBuffer.append(calendar.get(Calendar.YEAR)).append("-");        stringBuffer.append(calendar.get(Calendar.MONTH) + 1).append("-");        stringBuffer.append(calendar.get(Calendar.DAY_OF_MONTH)).append(" ");        stringBuffer.append(calendar.get(Calendar.HOUR_OF_DAY)).append(":");        stringBuffer.append(calendar.get(Calendar.MINUTE)).append(":");        stringBuffer.append(calendar.get(Calendar.SECOND)).append(":");        stringBuffer.append(calendar.get(Calendar.MILLISECOND));        System.out.println(stringBuffer);    }}