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1. 字符串 转换成日期类型

@Test

public void test1() {

String dateString = “2017-12-28 21:14:00”;

SimpleDateFormat dateFormat = new SimpleDateFormat(“yyyy-MM-dd HH:mm:ss”);

Date dateTime = null;

try {

dateTime = dateFormat.parse( dateString );

} catch (ParseException e) {

dateTime = null;

}// END TRY

System.out.println(dateTime);//Thu Dec 28 21:14:00 GMT+08:00 2017

}

2.取得前几天的日期

@Test

public void test1() {

Date d = new Date();//获取当前时间 Mon Jan 04 10:10:38 GMT+08:00 2018

int day = 3;//表示前3天

Calendar now = Calendar. getInstance ();

now.setTime(d);

now.set(Calendar.DATE, now.get(Calendar.DATE) – day);

System.out.println(now.getTime());//Mon Jan 01 10:10:38 GMT+08:00 2018

}