代码：
public class Demo01Calendar { public static void main(String[] args) { Calendar c=Calendar.getInstance();//多态。//获取日历信息 System.out.println(c); System.out.println(c.get(Calendar.YEAR));//获取年份 System.out.println(c.get(Calendar.MONTH));//获取月份 System.out.println(c.get(Calendar.DATE));//获取天 demo01();//设置时间 demo02();//给时间增加或者减少 demo03();//将日历改为日期 } public static void demo01() { Calendar c=Calendar.getInstance();//多态。//获取日历信息 System.out.println(c); c.set(Calendar.YEAR,2017); System.out.println(c.get(Calendar.YEAR));//获取上面赋值的年份 System.out.println(c.get(Calendar.MONTH));//获取月份 System.out.println(c.get(Calendar.DATE));//获取天 } public static void demo02() { Calendar c=Calendar.getInstance();//多态。//获取日历信息 System.out.println(c); c.add(Calendar.YEAR,2017);//增加年份 c.add(Calendar.MONTH,-3); System.out.println(c.get(Calendar.YEAR));//获取上面赋值的年份 System.out.println(c.get(Calendar.MONTH));//获取月份 System.out.println(c.get(Calendar.DATE));//获取天 } public static void demo03() { Calendar c=Calendar.getInstance(); Date date=c.getTime(); System.out.println(date); } }