java如何获取当前时间以及如何进行格式化？

public void testDate() {
    //SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");//设置日期格式

    Date date = new Date();
    String dateString = date.toString();
    long times = date.getTime();
    System.out.println("date.toString():"+date.toString());
    System.out.println("当前时间戳（毫秒）：" + times);

    Calendar c = Calendar.getInstance();
    System.out.println("当前日期：" + c.get(Calendar.DATE));
    System.out.println("当前年份:" + c.get(Calendar.YEAR));
    //月份从0开始，0-11
    System.out.println("当前月份:" + c.get(Calendar.MONTH));
    //12小时制，0-11
    System.out.println("12小时制：当前小时：" + c.get(Calendar.HOUR));
    System.out.println("24小时制：当前小时：" + c.get(Calendar.HOUR_OF_DAY));
    System.out.println("当前分钟：" + c.get(Calendar.MINUTE));
    System.out.println("当前秒：" + c.get(Calendar.SECOND));
    System.out.println("一年中的某天：" + c.get(Calendar.DAY_OF_YEAR));
    System.out.println("当前时间戳(毫秒）：" + c.getTimeInMillis());
    System.out.println("Calendar的toString()方法一般用作调试："+c.toString());
    SimpleDateFormat df = new SimpleDateFormat("yyyyMMdd");
    String currentDateStr = df.format(new Date());
    System.out.println("当前日期yyyyMMdd:"+currentDateStr);

}