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));
}