Java如何获取当前年份、月份和日期字符串

Calendar calendar = Calendar.getInstance();

// 获取当前年
int year = calendar.get(Calendar.YEAR);  
// 获取当前月
int month = calendar.get(Calendar.MONTH) + 1;  
// 获取当前日
int day = calenedar.get(Calendar.DATE);  
// 获取当前小时
int hour = calendar.get(Calendar.HOUR_OF_DAY);  
// 获取当前分钟
int minute = calendar.get(Calendar.MINUTE);  
// 获取当前秒
int second = calendar.get(Calendar.SECOND);  
// 获取当前是本周第几天
int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);  
// 获取当前是本月第几天
int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);  
// 获取当前是本年第几天
int dayOfYear = calendar.get(Calendar.DAY_OF_YEAR);

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  
// 获取当月第一天
calendar = Calendar.getInstance();
calendar.add(Calendar.MONTH, 0);
calendar.set(Calendar.DAY_OF_MONTH, 1);  
String firstday = format.format(calendar.getTime());  
// 获取当月最后一天
calendar = Calendar.getInstance();  
calendar.add(Calendar.MONTH, 1);  
calendar.set(Calendar.DAY_OF_MONTH, 0);  
String lastday = format.format(calendar.getTime());  
// 打印结果字符串
System.out.println("本月第一天和最后一天分别是：" + firstday + " 和 " + lastday + "。");

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
Date date = new Date(); 
System.out.println("当前日期字符串：" + format.format(date) + "。");

public static Long getPreviousWeekday(int hour) {
        int week = -1;
        int mondayPlus = getMondayPlus();
        GregorianCalendar currentDate = new GregorianCalendar();
        currentDate.add(Calendar.DATE, mondayPlus + 7 * week);
        Date monday = currentDate.getTime();
        TimeZone curTimeZone = TimeZone.getTimeZone("GMT+8");
        Calendar c = Calendar.getInstance(curTimeZone);
        c.setTime(monday);
        c.set(Calendar.HOUR_OF_DAY, hour);
        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);
       // Date z = c.getTime();
       // SimpleDateFormat sdf = new SimpleDateFormat(yyyy_MM_dd);
       // System.out.println(sdf.format(z));
        return  c.getTime().getTime();
    }
public static int getMondayPlus() {
        Calendar cd = Calendar.getInstance();
        int dayOfWeek = cd.get(Calendar.DAY_OF_WEEK) - 1;
        if (dayOfWeek == 1) {
            return 0;
        }
        return (1 - dayOfWeek);
    }