Question

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String, StringBuffer, and StringBuilder

what is the difference (advantages, disadvantages) between using StringBuilder instead String

StringBuilder text = new StringBuilder();
String cadena = "";
Scanner scanner = new Scanner(new FileInputStream(fFileName), fEncoding);
try {
  while (scanner.hasNextLine()) {
    String line = scanner.nextLine();
    text.append(line);
    cadena += line;
  }
} finally {
  scanner.close();
}    

Answer 1

It’s faster, but isn’t thread-safe.

You can build strings basically three ways.

1. by just concatenating strings (“foo” + “bar”) – slowest
2. by using StringBuffer, which is thread-safe, and faster than #1
3. by using StringBuilder, which is the fastest of all, but not thread-safe

Some other distinctions:

String: Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Concatenating strings using the + operator doesn’t modify the Strings involved, it creates a new String that is a combination of the Strings you’re concatenating.

StringBuffer: A thread-safe, mutable sequence of characters. A string buffer is like a String, but can be modified.

StringBuilder: A mutable sequence of characters. This class provides an API compatible with StringBuffer, but with no guarantee of synchronization.