java，c#将秒转换为hh:MM:ss的实现

/**
* 对时间进行转换
* @param time
* @return
*/
public static String secToTime(String str) {

if (str.equals("") || null==str) {
str="0";
}
Long long1 = (long) Math.floor(Double.parseDouble(str));
int time = Integer.parseInt(long1+"");
String timeStr = null;
int hour = 0;
int minute = 0;
int second = 0;
if (time <= 0)
return "00:00:00";
else {
minute = time / 60;
if (minute < 60) {
second = time % 60;
timeStr ="00:"+unitFormat(minute) + ":" + unitFormat(second);
} else {
hour = minute / 60;
if (hour > 99)
return "99:59:59";
minute = minute % 60;
second = time - hour * 3600 - minute * 60;
timeStr = unitFormat(hour) + ":" + unitFormat(minute) + ":" + unitFormat(second);
}
}
return timeStr;
}

/**
* 将传入的值进行转换
* @param i
* @return
*/
public static String unitFormat(int i) {
String retStr = null;
if (i >= 0 && i < 10)
retStr = "0" + Integer.toString(i);
else
retStr = "" + i;
return retStr;
}