Java基础-Date和SimpleDateFormat

public class DateTools {

public static final String DATE_FORMAT_FULL = "yyyy-MM-dd HH:mm:ss";  

/**
 * 日期转为格式化的字符串
 * @param time
 * @param format
 * @return String
 */
public static String formatDateToString(Date time,String format){
    SimpleDateFormat sdf = new SimpleDateFormat(format);

    return sdf.format(time);
}

/**
 * 按照制定格式format将date转换为相应的时间格式
 * @param date
 * @param format
 * @return Date
 */
public static Date formatStringToDate(String date,String format){
    SimpleDateFormat sdf = new SimpleDateFormat(format);
    try {
        return sdf.parse(date);
    } catch (ParseException e) {
        e.printStackTrace();
        throw new RuntimeException(e.toString()); 
    }
}

/**
 * 获取系统时间的毫秒值
 * @param format
 * @return String
 */
public static long getNowTimeMills(){
    Date day=new Date();    
    return day.getTime();
}

/**
 * 获取某时间的毫秒值
 * @param date
 * @param format
 * @return long
 */
public static long getTimeMills(String date,String format){
    SimpleDateFormat sdf = new SimpleDateFormat(format);
    Date day;
    try {
        day = sdf.parse(date);
    } catch (ParseException e) {
        e.printStackTrace();
        throw new RuntimeException(e.toString()); 
    }
    return day.getTime();
}

/**
 * 时间差
 * @param t1
 * @param t2
 * @return long
 */
public static long compareTime(long t1,long t2){
    if(t1 == t2){
        return 0;
    }else {
        return t1-t2;
    }
}

/**
 * 根据时间差得到发布日期信息
 * @param result
 * @return String
 */
public static String getResult(long result){

    if(result == 0){
        return "刚刚发布";
    }else if(result > 0){
        long time = result/(1000*3600);
        //System.out.println(time);
        if(time < 1){
            return "刚刚发布";
        }else if(time < 24){
            return time+"小时前发布";
        }else if(time < 148){
            return time/24+"天前发布";
        }else{
            return "1";
        }
    }else if(result < 0){
        return "";
    }
    return "";
}

}
—————–测试———————
public class Test {

public static void main(String[] args) {
    Product[] pro = new Product[5];
    pro[0] = new Product("1001","桃","2018-04-18 00:30:01");
    pro[1] = new Product("1002","西瓜","2018-04-17 19:30:01");
    pro[2] = new Product("1003","橙子","2018-04-17 09:30:01");
    pro[3] = new Product("1004","梨","2018-03-17 09:30:01");
    pro[4] = new Product("1005","苹果","2018-04-15 09:30:01");
    Date day;
    for(int i = 0; i < pro.length; i++){
        String time = pro[i].getUploadTime();
        day = DateTools.formatStringToDate(time, DateTools.DATE_FORMAT_FULL);
        long mills = DateTools.getTimeMills(time, DateTools.DATE_FORMAT_FULL);
        long nowMills = DateTools.getNowTimeMills();
        long result = DateTools.compareTime(nowMills, mills);
        String res = DateTools.getResult(result);
        if("1".equals(res)){
            System.out.println(pro[i].getProductId()+"，"+pro[i].getProductName()+"，"+DateTools.formatDateToString(day, DateTools.DATE_FORMAT_FULL));
        }else{
            System.out.println(pro[i].getProductId()+"，"+pro[i].getProductName()+"，"+res);
        }

    }
}

}
————运行结果————–