Javaは初日と各月の最終日を取得します

    // 获取当前年份、月份、日期
    Calendar cale = null;
    cale = Calendar.getInstance();
    // 获取当月第一天和最后一天
    SimpleDateFormat formatTemp = new SimpleDateFormat("yyyy-MM-dd");
    String firstday, lastday;
    // 获取当前月的第一天
    cale = Calendar.getInstance();
    cale.add(Calendar.MONTH, 0);
    cale.set(Calendar.DAY_OF_MONTH, 1);
    firstday = formatTemp.format(cale.getTime());
    // 获取当前月的最后一天
    cale = Calendar.getInstance();
    cale.add(Calendar.MONTH, 1);
    cale.set(Calendar.DAY_OF_MONTH, 0);
    lastday = formatTemp.format(cale.getTime());
    System.out.println("firstday:"+firstday+" lastday:"+lastday);
    
    //控制台输出
    //firstday:2019-07-01 lastday:2019-07-31