java获取当前月第一天和最后一天，上个月第一天和最后一天

╰+哭是因爲堅強的太久メ 2023-07-10 05:10 26阅读 0赞

java获取当前月第一天和最后一天，上个月第一天和最后一天  
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);
         
        /** 
     * 字符串的日期格式的计算 
     */ 
    public static int daysBetween(String smdate,String bdate) throws ParseException{ 
            SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd"); 
            Calendar cal = Calendar.getInstance(); 
            cal.setTime(sdf.parse(smdate)); 
            long time1 = cal.getTimeInMillis(); 
            cal.setTime(sdf.parse(bdate)); 
            long time2 = cal.getTimeInMillis(); 
            long between_days=(time2-time1)/(1000*3600*24); 
            return Integer.parseInt(String.valueOf(between_days));

\}  
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