Setting System Properties : System Properties « Development « Java Tutorial

1. Java Tutorial
2. Development
3. System Properties

public class MainClass {
  public static void main(String[] a) {
    String oldValue = System.clearProperty("java.class.path");
    System.setProperty("user.dir", "C:/MyProg");
    System.out.println(System.getProperty("user.dir"));
  }
}

C:/MyProg