每天一道剑指offer-替换空格

import java.util.*;
public class Solution {
    public String replaceSpace(StringBuffer str) {
        String str1 = str.toString();
        if(str1.equals(""))
            return str1;
        char [] strArray = str1.toCharArray();
        int i =0;
        int lengthSpace = 0;
        while(i < strArray.length)
        {
            if(strArray[i] == ' ')
                lengthSpace++;
            i++;
        }
        int newStrLength = strArray.length + lengthSpace*2;
        char [] newStr = new char[newStrLength];
        int j = newStrLength-1;
        i = strArray.length - 1;
        while(i >= 0)
        {
            if(strArray[i] !=  ' ')
            {
                newStr[j--] = strArray[i--];
            }else{
                newStr[j--] = '0';
                newStr[j--] = '2';
                newStr[j--] = '%';
                i--;
            }
        }
        return new String(newStr);
    }
}