java这种语法是啥意思？菜鸟问题

Question

这么写是什么意思？
a a=new a(){};
大括号里代表什么？

Answer 1

{}大括号里有n多代码的，这里是源代码
Thread t = new Thread() {
                                                  Socket client_connection = serverSocket.accept();
                                                  public void run() {
                                                            try {
                                                                      InputStream input =
                                                                                client_connection.getInputStream();
                                                                      OutputStream output =
                                                                                client_connection.getOutputStream();
                                                                      BufferedReader rd =
                                                                                new BufferedReader(
                                                                                          new InputStreamReader(input));
                                                                      String line = rd.readLine();
                                                                      HashMap header = new HashMap();
                                                                      do {
                                                                                line = rd.readLine();
                                                                                if (line.length() == 0) {
                                                                                          break;
                                                                                }
                                                                                int idx = line.indexOf(":");
                                                                                if (idx >= 0) {
                                                                                          String name = line.substring(0, idx).trim();
                                                                                          String value =
                                                                                                    line.substring(idx + 1).trim();
                                                                                          header.put(name, value);
                                                                                } else {
                                                                                          System.err.println(
                                                                                                    "Unknown header : " + line);
                                                                                }
                                                                      } while (true);
                                                                      String inum = (String) header.get("INUM");
                                                                      String address =
                                                                                client_connection
                                                                                          .getInetAddress()
                                                                                          .getHostAddress();
                                                                      Communicator c = new Communicator();
                                                                      c.service(address + inum, input, output);
                                                            } catch (IOException e) {
                                                                      e.printStackTrace();
                                                            } finally {
                                                                      if (client_connection != null) {
                                                                                try {
                                                                                          client_connection.close();
                                                                                } catch (IOException e1) {
                                                                                          e1.printStackTrace();
                                                                                }
                                                                      }
                                                            }
                                                  }
                                        };