How to use StringBuffer class

[Java Tip]

public class ImmutableStrings {

  public static void main(String[] args) {
    String foo = "foo";
    String s = "abc" + foo + "def" + Integer.toString(47);
    System.out.println(s);
    // The "equivalent" using StringBuffer:
    StringBuffer sb = new StringBuffer("abc"); // Creates String!
    sb.append(foo);
    sb.append("def"); // Creates String!
    sb.append(Integer.toString(47));
    System.out.println(sb);

  }
}