java 时间处理

		Date d1 = new Date(); 
		  
		Calendar   g = Calendar.getInstance();   
		g.setTime(d1);   
		g.add(Calendar.MONTH,-1);              
		Date d2 = g.getTime();   
		
		Calendar   g3 = Calendar.getInstance();   
		g3.setTime(d1);   
		g3.add(Calendar.MONTH,-2);              
		Date d3 = g3.getTime();  

 java 上个月

		DateFormat df1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  
		DateFormat df2 = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");  

                                  df1.format(df2.parse(str))

 格式化需要的样式