public class Test1 {    public static void main(String[]args){        System.out.println("时间为：\n"+getDate1()+"\n"+getDate2()+"\n"+getDate3()+"\n"+getDate4()+"\n"+getDate5());    }    /*    Calendar.HOUR_OF_DAY     24小时制    Calendar.HOUR     12小时制*/        //获取当天0点时间    public static String getDate1(){         Calendar cal = Calendar.getInstance();         cal.set(Calendar.HOUR_OF_DAY, 0);//控制时         cal.set(Calendar.MINUTE, 0);//控制分         cal.set(Calendar.SECOND, 0);//控制秒         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");         return sdf.format(cal.getTime());    }        //获取当天12点时间    public static String getDate2(){         Calendar cal = Calendar.getInstance();         cal.set(Calendar.HOUR_OF_DAY, 12);         cal.set(Calendar.MINUTE, 0);         cal.set(Calendar.SECOND, 0);         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");         return sdf.format(cal.getTime());    }            //获取本周一0点时间    public static String getDate3(){         Calendar cal = Calendar.getInstance();         cal.set(cal.get(Calendar.YEAR),cal.get(Calendar.MONDAY), cal.get(Calendar.DAY_OF_MONTH), 0, 0,0);         cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");         return sdf.format(cal.getTime());    }            //获取本月第一天0点时间    public static String getDate4(){         Calendar cal = Calendar.getInstance();         cal.set(cal.get(Calendar.YEAR),cal.get(Calendar.MONDAY), cal.get(Calendar.DAY_OF_MONTH), 0, 0,0);         cal.set(Calendar.DAY_OF_MONTH,cal.getActualMinimum(Calendar.DAY_OF_MONTH));         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");         return sdf.format(cal.getTime());    }             //获得本月最后一天24点时间    public static String getDate5(){         Calendar cal = Calendar.getInstance();         cal.set(cal.get(Calendar.YEAR),cal.get(Calendar.MONDAY), cal.get(Calendar.DAY_OF_MONTH), 0, 0,0);         cal.set(Calendar.DAY_OF_MONTH,cal.getActualMaximum(Calendar.DAY_OF_MONTH));         cal.set(Calendar.HOUR_OF_DAY, 24);         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");         return sdf.format(cal.getTime());    }         }