JAVA基础应用——日期/UUID等一些常用代码

日期

Date

Date d=new Date(); //当前时间对象

//大小比较
boolean flag = d.before(nowdate);
if(flag)
System.out.print("早于今天")
else
System.out.print("晚于今天")

类

SimpleDateFormat format = new SimpleDateFormat("yyyy.MM.dd H:m");
format.format(dateobject);   //把日期对象转成字符串

Date now = format.parse(dTime);   //把字符串转成日期对象

Calendar类

Calendar c = Calendar.getInstance();

c.setTime(Date date());
c.setTime(int year,int month, int day,int hour,int minute , int second);

Calendar c2 = Calendar.getInstance();
c2.set(1920, 13, 24, 22, 32, 22);

Date now = format.parse(dTime);
java.util.Calendar CalDelayDisable = java.util.Calendar.getInstance();
CalDelayDisable.setTime(now);
if (delay == 0)
{
String nowDateStr = format.format(now) + " 22:59:59";
Date nowDate2259 = format.parse(nowDateStr);
CalDelayDisable.setTime(nowDate2259);
//设置为当天的22点59分59秒
}
else
{
CalDelayDisable.add(Calendar.MINUTE, delay);
//设置为delay分钟后
}
Date effDate = CalDelayDisable.getTime();

Date now = new Date();
Date pre = getSpecifiedDayBefore(now);

private static Date getSpecifiedDayBefore(Date date)
{
Calendar c = Calendar.getInstance();

c.setTime(date);
int hour = c.get(Calendar.HOUR);
c.set(Calendar.HOUR, hour - 12);

Date dayBefore = c.getTime();
return dayBefore;
}

GregorianCalendar类

GregorianCalendar gC = new GregorianCalendar( int year,int month, int day,int hour,int minute , int second ) ;//方法可重载,具体看API

UUID使用

String uuid = UUID.randomUUID().toString();