java io 流

流:
按方向分:
1 輸入流:(往內存裏流的) 以內存爲基礎
2 輸出流:(從內存裏往外流的) 以內存爲基礎

按性質分:
1 字節流:以字節的形式存儲的 (看不懂的,或者不需要看)
2 字符流:以字符的形式存儲的(字符流是有編碼的,人能看懂,需要看)

如:文本文件:是字符的,如果是字節的,就看不懂咯.凡是能用記事本看的,都是字符流
txt,bat,java 用字符流
jpg,mp3,class 等格式,用記事本打開,根本看不懂,也不需要看,一般使用字節流

按方向加性質分:
1.以Stream結尾的都是字節流
2.以Reader或Writer結尾的都是字符流

輸入字節流:InputStream
輸出字節流:OutputStream

輸入字符流:Reader
輸出字符流:Writer

1 讀取一個文本文件從控制檯顯示:(方向:從磁盤到內存)使用輸入字符流
2 複製一個mp3文件: (方向:先從磁盤到內存,再從內存到磁盤)使用輸入字節流,輸出字節流(不需要看懂)
3 複製一個java文件:(方向:先從磁盤到內存,再從內存到磁盤)使用輸入字節流,輸出字節流(能看懂,但不需要看)
4 複製一個java文件,並在控制檯顯示:使用輸入字符流,輸出字符流(能看懂,需要看)

例:讀取一個文本文件 分析使用字符流Reader
物理文件-->File (JVM)-->FileReader --->BufferedReader


File-->FileInputStream -->BufferedInputStream --> ObjectInputStream
字節流轉成字符流FileInputStream --> InputStreamReader-->BufferedReader
File --> FileReader -->BufferedReader

File-->FileOutputStream --> BufferedOutputStream -->ObjectOutputStream
字節流轉成字符流FileOutputStream --> OutputStreamWriter-->BufferedWriter
File --> FileWriter -->BufferedWriter-->PrintWriter

注:使用緩衝,效率會更高.

序列化(持久化):把對象寫到磁盤或數據庫,或者到網絡裏.
反序列化:從磁盤或數據庫或網絡裏讀對象

DataInputStream ,DataOutputStream:用於在網絡中的傳輸

package com.inetpsa.kor.flowmodeler.partnerintegration.batch;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
/**
 *
 * @author e371575
 * @version $Rev$
 * @since Mar 21, 2011
 * 流(Stream)
 */
public class ReadFile {
	//讀取文本文件夾
	public static void readFile(String fileName){
		//定義緩衝字符輸入流
		BufferedReader in = null;
        try {
        	//將字節流轉爲 字符流:inputStreamReader,outputStreamWriter,網絡傳輸都是字節流 
        	in = new BufferedReader(new InputStreamReader(new FileInputStream(new File(fileName)), "gbk"));
        	// in = new BufferedReader(new FileReader(new File(fileName)));//這樣讀會產生中文亂碼
		//定義一行,用於存儲每行讀到的內容
		String line = null;
		//讀文件
		while((line = in.readLine()) != null){
			//輸出到控制檯
			System.out.println(line);
		}
        } catch (IOException e) {
	        e.printStackTrace();
        }
        finally{
        	try {
	            in.close();
            } catch (IOException e) {
	            e.printStackTrace();
            }
        }
	}
	public static void main(String[] args) throws IOException {
		//new ReadFile().readFile("c:/zhanghy/光盤使用說明.txt");
		new ReadFile().writeFile("c:/zhanghy/光盤使用說明2.txt");
		//new ReadFile().copyFile("c:/zhanghy/music/韓超-葬愛.mp3","c:/zhanghy/韓超-葬愛.mp3");
    }
	//將文本寫到文件
	public static void writeFile(String fileName){
		//定義緩衝字符輸出流 printwriter的方法比bufferedWriter更多點.所以一般可以使用它
		PrintWriter out = null;
	        try {
	        	//true表示追加文件
	            out = new PrintWriter(new BufferedWriter(new FileWriter(fileName,true)));
	            //輸出到文件
	            out.println("hello world 你好");
	            out.flush();//將管道中剩下的內容寫入目標
            } catch (IOException e) {
	            e.printStackTrace();
            }finally{
            	out.close();//自動調用flush()
            }
	}
	//copy file 使用輸入字節,輸出字節流
	public static void copyFile(String sourceFile,String targetFile){
		File source = new File(sourceFile);
		File target = new File(targetFile);
		BufferedInputStream in = null; //定義緩衝字節輸入流
		BufferedOutputStream out = null;//定義緩衝字節輸出流
		try{
			//輸入,字節數組 輸出
			in = new BufferedInputStream(new FileInputStream(source));
			out = new BufferedOutputStream(new FileOutputStream(target));
			byte[] buffer = new byte[1024];//定義一個byte[]數組,用於存儲文件中的內容
			//用於存儲臨時讀到的個數
			int readCount = 0;
			//讀:往buffer裏裝載,得到一個裝載量readCount
			while((readCount = in.read(buffer, 0, buffer.length))!= -1){
				//寫:讀多少,寫多少
				out.write(buffer, 0, readCount);
			}
			out.flush();//把緩衝區內容都寫到目標

		}catch(IOException e){
			e.printStackTrace();
		}finally{
			try {//先關out,再關in
				if(out != null){
					out.close();	
				}
	            if(in != null){
	            	in.close();
	            }
            } catch (IOException e) {
	            e.printStackTrace();
            }
		}
	}
}

package com.inetpsa.kor.flowmodeler.partnerintegration.batch;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

/**
 * @author e371575
 * @version $Rev$
 * @since Mar 22, 2011
 * 讀寫對象
 */
public class ReadWriterObject {
	public static void main(String[] args) {
	   // new ReadWriterObject().writeObjectToFile();
		new ReadWriterObject().ReadObjectFromFile();
    }
	//將一個動物對象寫到文件裏去,沒有被序列化的對象不能寫到文件裏
	public static void writeObjectToFile(){
		Animal an = new Animal();
		an.setAge(10);
		an.setName("xiaobai");
		//創建對象輸出流 ,
		try {
			//對象一定要實現序列化接口
	        ObjectOutputStream out = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(new File("c:/zhanghy/animal"))));
	        out.writeObject(an);//寫入對象
	        out.flush();//清空管道
		} catch (IOException e) {
	        e.printStackTrace();
	        System.out.println("write object error");
        } 
	}
	//讀從文件中對象
	public static void ReadObjectFromFile(){
		try {
	        ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(new FileInputStream(new File("c:/zhanghy/animal"))));
	        Object object = in.readObject();
	        System.out.println(object);
	        Animal an = (Animal)object;
	        System.out.println("age: "+an.getAge()+" name:"+an.getName());
	        in.close();
		} catch (Exception e) {
	        e.printStackTrace();
        }
	}
}
//動物類
class Animal implements Serializable{
	//定義版本號:用於在反序列化(也就是讀對象時,判斷該對象是否被修改過,如果不一致,則會讀取失敗)
	public static final long serialVersionUID = 6587245110917186266L;
	String name;
	int age;
    public String getName() {
    	return this.name;
    }
    public void setName(String name) {
    	this.name = name;
    }
    public int getAge() {
    	return this.age;
    }
    public void setAge(int age) {
    	this.age = age;
    }
	/**
     * {@inheritDoc}
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
	    return this.name+" | "+this.age;
    }

}