JAVA获取月第一天、最后一天

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
	//获取前一个月的第一天
	Calendar cal_1=Calendar.getInstance();//获取当前日期 
	cal_1.add(Calendar.MONTH, -1);
	cal_1.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天 
	String firstDay = format.format(cal_1.getTime());
	System.out.println("firstDay:"+firstDay); 
	//获取前一个月的最后一天
	Calendar cale = Calendar.getInstance(); 
	cale.set(Calendar.DAY_OF_MONTH,0);//设置为1号,当前日期既为本月第一天 
	String lastDay = format.format(cale.getTime());
	System.out.println("lastDay:"+lastDay);
	//获取当前月第一天：
	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 
	String first = format.format(c.getTime()); 
	System.out.println("first:"+first); 
	//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));
	String last = format.format(ca.getTime()); 
	System.out.println("last:"+last);