获取某月第一天和最后一天

Calendar   ca   =   Calendar.getInstance(); 

ca.setTime(new Date());   //   someDate   为你要获取的那个月的时间 

ca.set(Calendar.DAY_OF_MONTH,   1); 

Date   firstDate   =   ca.getTime(); 

ca.add(Calendar.MONTH,   1); 

ca.add(Calendar.DAY_OF_MONTH,   -1); 

Date   lastDate   =   ca.getTime();  

System.out.println(firstDate.toLocaleString());

System.out.println(lastDate.toLocaleString());