第二周周一

URL

统一资源定位器（网址），

从网址中读取一个图片，并写入文件中

public class Test3 {    public static void main(String[] args) {        try {            URL url = new URL("http://pic.nipic.com/2007-11-09/2007119122519868_2.jpg");            File fileImg = new File("f:\\11.jpg");            if(!fileImg.exists()){                fileImg.createNewFile();            }            OutputStream os = new FileOutputStream(fileImg);            InputStream is = url.openStream();            byte[] array = new byte[1024];            int i = is.read(array);            while(i!=-1){                os.write(array, 0, i);                i = is.read(array);            }            os.flush();            os.close();            is.close();        } catch (MalformedURLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

利用UDP协议发送数据报

public class MySend {    public static void main(String[] args) {        try {            DatagramSocket send = new DatagramSocket();            String s = "你好";            byte[] array = s.getBytes();            DatagramPacket packet = new DatagramPacket            (array,array.length,InetAddress.getByName("192.168.0.41"),8080);            System.out.println("开始发送");            send.send(packet);            send.close();        } catch (SocketException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch(UnknownException e){            e.printStackTrace();        }catch (IOException e){            e.printStackTrace();        }       }}

public class MyReceiver {    public static void main(String[] args) {        try {            DatagramSocket receiver = new DatagramSocket(8080);            byte[] array = new byte[1024];            DatagramPacket packet = new DatagramPacket(array,1024);            receiver.receive(packet);            byte[] data = packet.getData();            System.out.println("接收到的数据："+new String(data));            receiver.close();        } catch (SocketException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

完整版UDP协议发送 接受数据

public class MySend {    public static void main(String[] args) {        try {            DatagramSocket send = new DatagramSocket();            DatagramSocket receiver = new DatagramSocket(8080);            Scanner scanner = new Scanner(System.in);            byte[] receiverArray = new byte[1024];            while(true){            String s = scanner.next();            byte[] array = s.getBytes();            DatagramPacket packet = new DatagramPacket            (array,array.length,InetAddress.getByName("192.168.0.143"),8080);            System.out.println("Send开始发送："+s);            send.send(packet);            DatagramPacket packetReceiver = new DatagramPacket(receiverArray, receiverArray.length);            receiver.receive(packetReceiver);            byte[] data = packetReceiver.getData();            System.out.println("Send接收到的数据："+new String(data,0,packetReceiver.getLength()));            }        } catch (SocketException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch(UnknownException e){            e.printStackTrace();        }catch (IOException e){            e.printStackTrace();        }       }}

public class MyReceiver {    public static void main(String[] args) {        try {            DatagramSocket receiver = new DatagramSocket(8080);            DatagramSocket send = new DatagramSocket();            byte[] array = new byte[1024];            Scanner scanner = new Scanner(System.in);            while(true){            DatagramPacket packet = new DatagramPacket(array,1024);            receiver.receive(packet);//          byte[] data = packet.getData();            System.out.println("Receiver接收到的数据："+new String(array));            String sendString = scanner.next();            System.out.println("Receiver发送的数据"+sendString);            byte[] sendByte = sendString.getBytes();            DatagramPacket packetSend = new DatagramPacket            (sendByte, sendByte.length,InetAddress.getByName("192.168.0.41"),8081);            send.send(packetSend);            }        } catch (SocketException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

枚举

package com.lingzhuo.enums;public enum Sex {    FEMALE,MALE;    //相当于public static final int FEMALE = 0X1;}

XML解析

DOM解析

使用dom解析xml文档的步骤：
1、创建解析器工厂对象
2、由解析工厂对象创建解析器对象
3、由解析器对象对指定xml文件进行解析
4、以Document对象为起点对dom树的节点进行增删改查操作

SAX解析

Json解析

（必然会用到）

public class JSONTest {    public static void main(String[] args) {        String json = creatJSON();        JSONObject obj = JSONObject.fromObject(json);        System.out.println(obj.getJSONObject("city"));        JSONObject today = obj.getJSONObject("today");        JSONArray array = today.getJSONArray("index");        for (int i = 0; i < array.size(); i++) {            JSONObject obj1 = array.getJSONObject(i);            System.out.println(obj1.getString("name"));        }       }    private static String creatJSON(){        JSONObject obj = new JSONObject();        obj.put("city","北京");        obj.put("cityid","123");        JSONObject today = new JSONObject();        today.put("date", "2015-08-03");        today.put("week", "星期一");        JSONArray array = new JSONArray();        JSONObject index1 = new JSONObject();        index1.put("name", "感冒");        JSONObject index2 = new JSONObject();        index1.put("name", "防晒");        JSONObject index3 = new JSONObject();        index1.put("name", "炎热");        array.add(index1);        array.add(index2);        array.add(index3);        today.put("index", array);        obj.put("today", today);        System.out.println(obj.toString());        return obj.toString();      }}