Java's StringBuffer and StringBuilder classes represent strings that can be dynamically modified. : StringBuffer « Utility Classes « SCJP

1. SCJP
2. Utility Classes
3. StringBuffer

public class MainClass{
  public static void main(String[] argv){
    StringBuffer sb = new StringBuffer();
    sb.append(1);
    sb.append("asdf");
    System.out.println(sb.toString());
  }
}