int类型转换成String ， 不足n位 在前面补0

 1 private String secToTime(int time){
 2         String timeStr = null;  
 3         int hour = 0;  
 4         int minute = 0;  
 5         int second = 0;  
 6         if (time <= 0)  
 7             return "00:00";  
 8         else {  
 9             minute = time / 60;  
10             if (minute < 60) {  
11                 second = time % 60;  
12                 timeStr = String.format("%02d", minute) + ":" + String.format("%02d", second);  
13             } else {  
14                 hour = minute / 60;  
15                 if (hour > 99)  
16                     return "99:59:59";  
17                 minute = minute % 60;  
18                 second = time - hour * 3600 - minute * 60;  
19                 timeStr = String.format("%02d", hour) + ":" + String.format("%02d", minute) + ":" + String.format("%02d", second);  
20             }  
21         }  
22         return timeStr;  
23     }