剑指Offer 替换空格

public class Solution {
    public String replaceSpace(StringBuffer str) {
       StringBuffer result = new StringBuffer();
        int length = str.length();
        for(int i = 0;i<length;i++){
            if(str.charAt(i)!=' '){
                result.append(str.charAt(i));
            }else{
                result.append("%20");
            }
        }
        return new String(result);
    }
}