java获取当月第一天的零点零分和最后一天的23点59分

刚好写到需要获取数据库中当前月的所有记录，所以将该功能记下来！

Calendar c = Calendar.getInstance();
c.add(Calendar.MONTH, 0);
c.set(Calendar.DAY_OF_MONTH, 1);//设置为1号,当前日期既为本月第一天
//将小时至0
c.set(Calendar.HOUR_OF_DAY, 0);
//将分钟至0
c.set(Calendar.MINUTE, 0);
//将秒至0
c.set(Calendar.SECOND,0);
//将毫秒至0
c.set(Calendar.MILLISECOND, 0);
// 获取本月第一天的时间戳
System.out.println(c.getTimeInMillis());

//获取当前月最后一天
Calendar ca = Calendar.getInstance();
ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));
//将小时至0
ca.set(Calendar.HOUR_OF_DAY, 0);
//将分钟至0
ca.set(Calendar.MINUTE, 0);
//将秒至0
ca.set(Calendar.SECOND,0);
//将毫秒至0
ca.set(Calendar.MILLISECOND, 0);
// 获取本月最后一天的时间戳
System.out.println(ca.getTimeInMillis());