Java日期工具类的使用及方法

Calendar 日历

import java.util.Calendar; 导入类

该抽象类的定义如下：

public abstract class Calendar extends Object implements Serializable,
Cloneable, Comparable<Calendar>{
}

对应的静态类方法：

public static Calendar getInstance(){
Locale aLocale = Locale.getDefault(Locale.Category.FORMAT);
return createCalendar(defaultTimeZone(aLocale), aLocale);
}

import java.util.Calendar;
import java.util.Date;
public class Calendar1 {
public static void main(String[] args) {
//Calendar是一个抽象类，不允许直接实例化，
//Calendar c = new Calendar();
//getInstance() 是实例化。
Calendar c = Calendar.getInstance();
//c.set();
//c.get();
Date d1 = c.getTime(); //getTime() 方法，功能将当前Calendar实例对象，转换
为Date的实例对象
Date d2 = new Date();
System.out.printf("%tF %<tT%n",d1);
System.out.printf("%tF %<tT%n",d2);
long time = c.getTimeInMillis();//日历返回一个时间戳 是一个long的类型数字
}
}

基础的使用方法：

Calendar calendar = Calendar.getInstance();
System.out.println("当前时间: " + calendar.getTime());

public static final int ERA = 0;
public static final int YEAR = 1;//*****
public static final int MONTH = 2;//*****
public static final int WEEK_OF_YEAR = 3;
public static final int WEEK_OF_MONTH = 4;
public static final int DATE = 5;
public static final int DAY_OF_MONTH = 5;//*****
public static final int DAY_OF_YEAR = 6;
public static final int DAY_OF_WEEK = 7; //
public static final int DAY_OF_WEEK_IN_MONTH = 8;
public static final int AM_PM = 9;
public static final int HOUR = 10;//*****
public static final int HOUR_OF_DAY = 11;
public static final int MINUTE = 12;//*****
public static final int SECOND = 13;//*****
public static final int MILLISECOND = 14;
public static final int ZONE_OFFSET = 15;
public static final int DST_OFFSET = 16;
public static final int FIELD_COUNT = 17;

设置方法： set()

//请计算2001 6 18哪一天是星期？
Calendar c2 = Calendar.getInstance();
c2.set(Calendar.YEAR,2001);
c2.set(Calendar.MONTH,6-1);
c2.set(Calendar.DAY_OF_MONTH,18);
System.out.printf("%tF 这一日期是：%tA%n",c2,c2);

获取方法： get()方法

Calendar c = Calendar.getInstance();
System.out.println(c.get(1)); //传入一个1 返回一个年份 2022
System.out.println(c.get(Calendar.YEAR)); //传入一个1 返回一个年份 2022
System.out.println(c.get(2)+1);//返回月 7
System.out.println(c.get(Calendar.DAY_OF_MONTH)); //11 几号
System.out.println(c.get(5)); //11 几号