第二次作業

1.

2.

/**
 * The HelloWorldApp class implements an application that
 * simply prints "Hello World!" to standard output.
 */
class HelloWorldApp {
    public static void main(String[] args) {
        System.out.println("Hello World!"); // Display the string.
    }
}

3.

import java.net.*;

public class TestInet1 {
  public static void main(String argv[])
  {
    try {
      InetAddress myip = InetAddress.getLocalHost();

      System.out.println(myip.getHostName());
      System.out.println(myip.getHostAddress());
    } catch (UnknownHostException e) {
      System.out.println("Error: unable to resolve localhost");
    }
  }
}
                                                                        4.