替换空格

请实现一个函数，将一个字符串中的空格替换成“%20”。例如，当字符串为We Are Happy.则经过替换之后的字符串为We%20Are%20Happy。

方法1:replace函数

 public String replaceBackend(String word){
    String a = word.toString();
    String b = a.replaceAll(" ","%20");
    return b;
    }

方法2:转换成数组再去拼吧吧吧吧

       public String replaceBackend(String word){
            String a = word.toString();
            char[] b = a.toCharArray();
            StringBuffer c = new StringBuffer();
            for(int i = 0 ;i<b.length;i++){
                if(b[i] == ' '){
                    c.append("%20");
                }else{
                    c.append(b[i]);
                }
            }
                return c.toString();
                
            }
       public static void main(String args[]){
           String word = "we are happy";
           aaa a = new aaa();
           System.out.println(a.replaceBackend(word));
       }