Java实现id自增的字符串类型的数字编号

public class mainTest {

public static void main(String[] args) {
String outString="";
outString=fillStr("123", 9, false, "0");
System.out.println("false"+outString);
outString=fillStr("123", 9, true, "0");
System.out.println("true"+outString);

}
/**
*
* @param value
* @param count
* @param frontORback
* @param fillChar
* @return if frontORback is ture ,return the (count-value.length) fillchar added to the front of the value
* if frontORback is false,return the (count-value.length) fillchar added to the back of the value
* for instance : value="123",count=9,frontORback=true,fillchar="0"<br>
* return "123000000"
*
*/
private static String fillStr(String value, int count, boolean frontORback, String fillChar) {
String rtvalue = value;
if (rtvalue == null) {
rtvalue = "";
for (int i = 0; i < count; i++)
if (frontORback)
rtvalue = String.valueOf(rtvalue)
+ String.valueOf(fillChar);
else
rtvalue = String.valueOf(fillChar)
+ String.valueOf(rtvalue);
} else {
int len = rtvalue.length();
if (len > count) {
rtvalue = rtvalue.substring(0, count);
} else {
int a = count - len;
for (int i = 0; i < a; i++)
if (frontORback)
rtvalue = String.valueOf(rtvalue)
+ String.valueOf(fillChar);
else
rtvalue = String.valueOf(fillChar)
+ String.valueOf(rtvalue);
}
}
return rtvalue;
}
}