获取每月第一天最后一天 java

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd"); //获取前月的第一天
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
firstDay = format.format(cal_1.getTime());
System.out.println("-----1------firstDay:"+firstDay);
//获取前月的最后一天
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
lastDay = format.format(cale.getTime());
System.out.println("-----2------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);