public class EchoClient1 {
 public static void main(String args[])   {
   try{
      if (args.length != 1){
System.out.println("USAGE: java Client servername");
return;
      }
      String  connectto= args[0];
    Socket connection;
      // connect to server
      if(connectto.equals("localhost")){
connection=new Socket(InetAddress.getLocalHost(),8500);
      }
      else{
connection=new Socket(InetAddress.getByName(connectto),8500);
      }
      BufferedReader  input=new BufferedReader(new InputStreamReader(connection.getInputStream()));
      PrintWriter out = new PrintWriter(connection.getOutputStream(), true /* autoFlush */);

      // read information from server
      String info;
      info = input.readLine();
      System.out.println(info);
      boolean done = false;
      BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
      String sInput;
      while(!done){
         sInput = in.readLine();
         out.println(sInput);
         if (sInput.equalsIgnoreCase("bye")) done = true;
         info = input.readLine();
         System.out.println(info);
     }
     connection.close();
   }
   catch(SecurityException e){
     System.out.println("SecurityException when connecting Server!");
   }
   catch(IOException e){
     System.out.println("IOException when connecting Server!");
   }
 }
}

java 类名 参数1 参数2

其中，参数1就是args[0]，依次类推