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());