I found three ways to generate a prefix of a given string:

String s = ""
for(char c : word){
    String prefix = s + c;
}

or

StringBuilder sb = new StringBuilder()
for(char c : word){
    sb.append(c);
    String prefix = sb.toString();
}

or

for(int i = 1; i< s.length(); i++) {
    prefix = s.substring(0,i);
}

Is there any clear performance difference between these approaches? I read that substring is quite performant as it uses System.arrayCopy, I am also not sure how the standard concatenation operator is performing vs StringBuilder.