java 格式化日期字符串

1. 字符串转换为日期

public static Date parseDate(String strDate,String pattern){                            if(strDate==null || pattren==null ||        "".equals(strDate.trim()) ||"".equals(pattern.trim()) )){    throw new IllegalArgumentException("字符串或日期格式为空");    }    Date date = null;    try{    SimpleDateFormat parser = new SimpleDateFormat(pattern);            date=parser.parse(str);    }catch (ParseException e) {            System.out.println("格式化失败" + e.getMessage());        }    return date;}

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2. 日期格式化为字符串

public static String format(Date date, String pattern) {        if(date==null)        {            return "";        }        if (date == null || pattern == null || "".equals(pattern.trim()))            throw new IllegalArgumentException("日期或字符串格式为空");        String str = null;        try {            SimpleDateFormat parser = new SimpleDateFormat(pattern);            str = parser.format(date);        } catch (Exception e) {            System.out.println("不能转换" + e.getMessage());        }        return str;    }

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3. 把一种格式的日期字符串格式化成另一种格式的日期字符串

public static String format  (String str, String oldP, String newP) {        if (str == null || "".equals(str.trim()) || oldP == null                || "".equals(oldP.trim()) || newP == null                || "".equals(newP.trim()))            throw new IllegalArgumentException("不能为空");        return format(parseDate(str,oldP),newP);    }

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