Java 流的使用总结

1. InputStreamReader和BufferedReader将流转化为文本

1) 从url中读取资源将其转化为json(每日一句写法)

package com.json;import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;import net.sf.json.JSONObject;public class Json {
public static void main(String[] args) {try {URL webUrl = new URL("http://open.iciba.com/dsapi/");HttpURLConnection urlConnection = (HttpURLConnection)webUrl.openConnection();urlConnection.setRequestMethod("GET");urlConnection.connect();InputStream inputStream = urlConnection.getInputStream();InputStreamReader reader = new InputStreamReader(inputStream); BufferedReader breader = new BufferedReader(reader);String speck = null;StringBuffer str = new StringBuffer();while ((speck = breader.readLine())!= null) {str.append(speck);}JSONObject  dataJson=JSONObject.fromObject(str.toString());String  response=(String) dataJson.get("note");// JSONObject Json = JSONObject.fromObject(str.toString());System.out.println(response);} catch (Exception e) {e.printStackTrace();}
}
}

2) 从url中读取资源将其转化为xml(天气预报写法)

package com.xml;import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLEncoder;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;import javax.xml.parsers.*;import org.w3c.dom.Document;public class WeatherIo {private static final String getWeatherUrl = "http://php.weather.sina.com.cn/xml.php?password=DJOYnieT8234jlsK";public void getXml() throws Exception{// step 1: 获得dom解析器工厂（工作的作用是用于创建具体的解析器）DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();// step 2:获得具体的dom解析器DocumentBuilder db = dbf.newDocumentBuilder();String city = "武汉";city = URLEncoder.encode(city, "gb2312");String url = getWeatherUrl+"&city="+city+"&day=1";  URL webUrl = new URL(url);Document document = db.parse(webUrl.openStream()); InputStreamReader reader = new InputStreamReader(webUrl.openStream());BufferedReader breader = new BufferedReader(reader);//Document document = db.parse(webUrl.openStream());StringBuilder result = new StringBuilder();String line = null;while ((line=breader.readLine())!=null) {result.append(line);}System.out.println(result.toString());//解析document文件 取到一天的天气预报List onedayData = getOnedayData(document);}public List getOnedayData(Document document){try {List onedayData = new ArrayList();String  city = "";//城市String  status1 = "";//天气String  status2 = "";String  figure1 = "";//天气拼音String  figure2 = "";String  temperature1 = "";//温度String  temperature2 = "";String  direction1 = "";//风向String  direction2 = "";String  power1 = "";//风力String  power2 = "";String  savedate_weather  = "";//时间city = document.getElementsByTagName("city").item(0).getFirstChild().getNodeValue();if(document.getElementsByTagName("status1").item(0).getFirstChild()!=null){status1 = document.getElementsByTagName("status1").item(0).getFirstChild().getNodeValue();}if(document.getElementsByTagName("status2").item(0).getFirstChild()!=null){status2 = document.getElementsByTagName("status2").item(0).getFirstChild().getNodeValue();}if(document.getElementsByTagName("figure1").item(0).getFirstChild()!=null){figure1 = document.getElementsByTagName("figure1").item(0).getFirstChild().getNodeValue(); }if(document.getElementsByTagName("figure2").item(0).getFirstChild()!=null){figure2 = document.getElementsByTagName("figure2").item(0).getFirstChild().getNodeValue(); }if(document.getElementsByTagName("temperature1").item(0).getFirstChild()!=null){temperature1 = document.getElementsByTagName("temperature1").item(0).getFirstChild().getNodeValue();}if(document.getElementsByTagName("temperature2").item(0).getFirstChild()!=null){temperature2 = document.getElementsByTagName("temperature2").item(0).getFirstChild().getNodeValue();}if(document.getElementsByTagName("direction1").item(0).getFirstChild()!=null){direction1 = document.getElementsByTagName("direction1").item(0).getFirstChild().getNodeValue();}if(document.getElementsByTagName("direction2").item(0).getFirstChild()!=null){direction2 = document.getElementsByTagName("direction2").item(0).getFirstChild().getNodeValue();}if(document.getElementsByTagName("power1").item(0).getFirstChild()!=null){power1 = document.getElementsByTagName("power1").item(0).getFirstChild().getNodeValue();}if(document.getElementsByTagName("power2").item(0).getFirstChild()!=null){power2 = document.getElementsByTagName("power2").item(0).getFirstChild().getNodeValue();}savedate_weather = document.getElementsByTagName("savedate_weather").item(0).getFirstChild().getNodeValue();onedayData.add(city);onedayData.add(status1);onedayData.add(status2);onedayData.add(figure1);onedayData.add(figure2);onedayData.add(temperature1);onedayData.add(temperature2);onedayData.add(direction1);onedayData.add(direction2);onedayData.add(power1);onedayData.add(power2);onedayData.add(savedate_weather);SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  Date date = format.parse(savedate_weather);SimpleDateFormat dateFm = new SimpleDateFormat("EEEE");//星期格式String  xingqi = dateFm.format(date);onedayData.add(xingqi);return onedayData;} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();return null;}  }
}

2. ObjectInputStream和ObjectoutputStream

1) ObjectoutputStream将java对象bean实例化在本地磁盘上

package com.serializable_txt.file;import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;import com.serializable_txt.bean.Person;public class ObjectOutputStream1 {
public static void main(String[] args) throws FileNotFoundException, IOException {/**序列化，将对象保存在了本地硬盘上面 */Person pr1 = new Person("tom",18);Person pr2 = new Person("marry",20);Person pr3 = new Person("tomiay",18);File f = new File("c:ser1.txt");ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(f));out.writeObject(pr1);out.writeObject(pr2);out.writeObject(pr3);}
}

2) ObjectInputStream本地磁盘上文件读取为java对象bean

package com.serializable_txt.file;import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;import javax.imageio.stream.FileImageInputStream;import com.serializable_txt.bean.Person;@SuppressWarnings("unused")
public class ObjectInputStream2 {
public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {/**反序列化，读取本地硬盘上面信息，封装成对象 */File f = new File("c:ser1.txt");ObjectInputStream input = new ObjectInputStream(new FileInputStream(f));
//  Person pr1 = (Person) input.readObject();
//  System.out.println(pr1.getName());
//  Person pr2 = (Person) input.readObject();
//  System.out.println(pr2.getName());
//  Person pr3 = (Person) input.readObject();
//  System.out.println(pr3.getName());/** 循环读取，当出现EofException异常时，退出循环；*/while (true) {try {Person pr = (Person) input.readObject();System.out.println(pr.getName());} catch (Exception e) {if(e instanceof EOFException){break;}}}
}
}

3) 用到的bean(要序列化)

package com.serializable_txt.bean;import java.io.Serializable;
/** 序列化；标记接口*/
public class Person implements Serializable{
private String name;
private int age;
public String getName() {return name;
}
public void setName(String name) {this.name = name;
}
public int getAge() {return age;
}
public void setAge(int age) {this.age = age;
}
public Person() {
}
public Person(String name, int age) {this.name = name;this.age = age;
}}

3. DataInputStream和DataOutputStream

1) 存储和读取所实例化的对象的属性

package com.serializable_txt.file;import java.io.*;import com.serializable_txt.bean.Member;public class DataStreamDemo
{public static void main(String[] args) {Member[] members = {new Member("Justin",90),new Member("momor",95),new Member("Bush",88)};try{DataOutputStream dataOutputStream = new DataOutputStream(new FileOutputStream(new File("f://members.txt")));for(Member member:members){//写入UTF字符串dataOutputStream.writeUTF(member.getName());//写入int数据dataOutputStream.writeInt(member.getAge());}//所有数据至目的地dataOutputStream.flush();//关闭流dataOutputStream.close();DataInputStream dataInputStream = new DataInputStream(new FileInputStream(new File("f://members.txt")));//读出数据并还原为对象for(int i=0;i<members.length;i++){//读出UTF字符串String name = dataInputStream.readUTF();//读出int数据int score = dataInputStream.readInt();members[i] = new Member(name,score);}//关闭流dataInputStream.close();//显示还原后的数据for(Member member : members){System.out.printf("%s\t%d%n",member.getName(),member.getAge());}}catch(IOException e){e.printStackTrace();}}
}

2) 用到的bean

package com.serializable_txt.bean;public class Member {private String name;private int age;public Member() {}public Member(String name, int age) {this.name = name;this.age = age;}public void setName(String name) {this.name = name;}public void setAge(int age) {this.age = age;}public String getName() {return name;}public int getAge() {return age;}
}

4.PushbackInputStream流的使用

package net.nyist.io;import java.io.FileReader;
import java.io.IOException;
import java.io.PushbackReader;
import java.security.acl.Permission;public class PushBackTest {public static void main(String[] args) {try (// 创建一个PushbackReader对象，指定推回缓冲区的长度为64PushbackReader pr = new PushbackReader(new FileReader("src/net/nyist/io/PushBackTest.java"), 64);) {char[] buf = new char[32];// 用以保存上次读取字符串的内容String lastContent = "";int hasRead = 0;// 循环读取文件内容while ((hasRead = pr.read(buf)) > 0) {// 将读取的内容转化为字符串String content = new String(buf, 0, hasRead);int targetIndex = 0;// 将上次读取的字符串和本次读取的字符串拼接起来// 查看是否包含目标字符串，// 如果包含目标字符串if ((targetIndex = (lastContent + content).indexOf("new PushbackReader")) > 0) {// 将本次的内容和上次的内容一起推回缓冲区pr.unread((lastContent + content).toCharArray());// 重现定义一个长度为targetIndex的char类型的数组if (targetIndex > 32) {buf = new char[targetIndex];}// 再次读取指定长度的内容，即目标字符串之前的内容pr.read(buf, 0, targetIndex);// 答应读取指定长度的内容System.out.println(new String(buf, 0, targetIndex));System.exit(0);} else {// 打印上次读取的内容System.out.println(lastContent);// 将本次读取的内容设置为上次读取的内容lastContent = content;}}} catch (IOException ioe) {ioe.printStackTrace();}}}

5.ByteArrayOutputStream的使用实现byte转化在socket中,会常用这个

public static byte[] readStream(InputStream inStream) throws Exception{ByteArrayOutputStream outSteam = new ByteArrayOutputStream();byte[] buffer = new byte[1024];int len = -1;while( (len=inStream.read(buffer)) != -1){outSteam.write(buffer, 0, len);}outSteam.close();inStream.close();return outSteam.toByteArray();//new String (outSteam.toByteArray());}

**重点**

所有inputStream的read()方法,是一个字节的读取,而read(byte[])将返回的是读取了多少个字节

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