时间日期的获取

public class DateZaXiang {
    public static void main(String[] args){
        //先回顾一下怎么获取时间
        Calendar ca=Calendar.getInstance();//获取日历
        System.out.println(ca.get(Calendar.YEAR));//获取当前年份
        System.out.println(ca.get(Calendar.MONTH)+1);//获取当前月份
        System.out.println(ca.get(Calendar.DAY_OF_MONTH));//获取当月中的当前天
        System.out.println(ca.get(Calendar.DAY_OF_WEEK_IN_MONTH));//获取当周中的当前天
        
        //获取前一天的日期，将前一天日期添加到日历中即可
        ca.add(Calendar.DAY_OF_MONTH, -1);
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
        System.out.println(sdf.format(ca.getTime()));
        
        //数字格式化器,左边补0
        int s=123;
        DecimalFormat df=new DecimalFormat("0000");
        System.out.println(df.format(s));
        
    }
}

public class DateZaXiang {public static void main(String[] args){//先回顾一下怎么获取时间Calendar ca=Calendar.getInstance();//获取日历System.out.println(ca.get(Calendar.YEAR));//获取当前年份System.out.println(ca.get(Calendar.MONTH)+1);//获取当前月份System.out.println(ca.get(Calendar.DAY_OF_MONTH));//获取当月中的当前天System.out.println(ca.get(Calendar.DAY_OF_WEEK_IN_MONTH));//获取当周中的当前天//获取前一天的日期，将前一天日期添加到日历中即可ca.add(Calendar.DAY_OF_MONTH, -1);SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");System.out.println(sdf.format(ca.getTime()));//数字格式化器,左边补0int s=123;DecimalFormat df=new DecimalFormat("0000");System.out.println(df.format(s));}}