剑指offer---替换空格

public class Solution {
    public String replaceSpace(StringBuffer str) {
        String str1 = str.toString();
        char[] charArray = str1.toCharArray();
        StringBuffer sBuffer = new StringBuffer();
        for(char c : charArray){
            if(c == ‘ ‘){
                sBuffer.append("%20");
            } else{
                sBuffer.append(c);
            }
        }
        String string = sBuffer.toString();
        return string;
    }
}