急，求高手解决

1 根据规律写方法

numIncre(“000000”) => “000001”

numIncre(”0023") => “0024”

numIncre(“0009”) => “0010”

numIncre(“000099”) => “000100”

numIncre(“9”) => “0”

public static String numIncre(String num);

2根据规律写方法

round(123.455,2) => 123.46

round(123.449,2) => 123.45

round(123.44,3) => 123.440

round(123.4455,3) => 123.446

round(123.4499,3) => 123.450

round(123.9,0) => 124

public static double strRound(double value,int decimalPlaces);
[b]问题补充：[/b]
我要实现代码

import java.math.BigDecimal;

public class ts_main {

public static void main(String args[]) {
    System.out.println(numIncre("00019"));
    System.out.println(strRound(123.455,2)) ;
}

public static String numIncre(String str) {
    return insertStr(getTotal(str), str.length()) + getTotal(str);
}

public static String insertStr(String _total, int num) {
    String _str = "";
    if (_total.length() < num) {
        for (int i = 0; i < num - _total.length(); i++) {
            _str += "0";
        }
    }
    return _str;
}

public static String getTotal(String str) {
    return Integer.parseInt(str) + 1 + "";
}

public static double strRound(double value,int decimalPlaces) {
    if (decimalPlaces < 0){
        throw new IllegalArgumentException(
         "The scale must be a positive integer or zero");
    }
    BigDecimal b = new BigDecimal(Double.toString(value));
    BigDecimal one = new BigDecimal("1");
    return b.divide(one, decimalPlaces, BigDecimal.ROUND_HALF_UP).doubleValue();
}

}

第一个,简单,加一,保留相同位数.
第二个,就是四舍五入,求精度问题.