SimpleDateFormat

date --> text

Date now = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String strDate = sdf.format(now);
System.out.println(strDate);

Date now = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");
String strDate = sdf.format(now);
System.out.println(strDate);

Date now = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
String strDate = sdf.format(now);
System.out.println(strDate);

text --> date

//由字符串解析成Date对象

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
try
{
    Date date = sdf.parse("2018-10-10");
    System.out.println(date);
}
catch (ParseException e)
{
    System.out.println("时间解析出错啦：" + e.getMessage());
}

Method

String format(Date date)

    把Date格式化为字符串Formats a Date into a date/time string.

Date parse(String source)

    把字符串解析为Date

    Parses text from the beginning of the given string to produce a date.

Java的SimpleDateFormat类