每次用到IO的讀寫檔案都老忘記寫法，都要翻過往筆記，今天總結下，省的以後老忘。java讀寫檔案的IO流分兩大類，位元組流和字元流，基類分別是字元：Reader和Writer；位元組：InputStream和OutPutStream，

1、字元流分為FileReader和FileWrtier，這兩個的父類是InputStreamReader和OutStreamWrtier

2、位元組流分為FileInputStream和FileOutPutStream

關係網：

Reader->InputStreamReader->FileReader

Reader->BufferedReader

Writer->OutputStreamWriter->FileWriter

Writer->BufferedWriter

InputStream->FileInputStream。FileInputStream 用於讀取諸如影象資料之類的原始位元組流。要讀取字元流，請考慮使用 FileReader。

InputStream->FilterInputStream->BufferedInputStream

OutputStream->FileOutputStream。FileOutputStream 用於寫入諸如影象資料之類的原始位元組的流。要寫入字元流，請考慮使用 FileWriter

OutputStream->FilterOutputStream->BufferedOutputStream

流的程式一般分以下四步：

1.建立檔案物件 File file = new File("xxx.txt");

2.用流裝載檔案 FileReader fr = new FileReader(file);

3.如果用緩衝區，則用緩衝區裝載流，用緩衝區是為了提高讀寫效能 BufferReader br = new BufferReader(fr);

4.開始讀寫操作 String s = null; StringBuffer sb = new StringBuffer(); while((s=br.readLine()!=null) { sb.append(s); } 如果遇到位元組流要轉換成字元流，則在緩衝區前加一步 InputStreamReader isr = new InpuStreamReader(InputStream in); 或者需要編碼轉換的，則在緩衝區前加一步 InputStreamReader isr = new InpuStreamReader(InputStream in，Charset cs);

下面的程式碼分別是複製文字檔案、影象檔案。位元組轉換字元的操作：

package com.io;

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.UnsupportedEncodingException;

import com.sun.org.apache.bcel.internal.generic.NEW;

/**

 * @author QiaoJiafei

 * @version 建立時間：2016年4月12日 下午12:03:37

 * 類說明

 */

public class TestIO {

    public static void main(String[] args) throws IOException {

        testFileReader();

        testFileInputStream();

    }

    private static void testInputStream() throws IOException {

        InputStream ist = System.in;

        BufferedReader br = new BufferedReader(new InputStreamReader(ist,"uft-8"));

        String s = "";

        while ((s=br.readLine())!=null) {

            System.out.println(s);

        }

        br.close();

    }

    private static void testFileReader() throws IOException {

        FileReader reader = new FileReader("/Users/qiaojiafei/Documents/test.txt");

        FileWriter writer = new FileWriter("/Users/qiaojiafei/Documents/test_copy.txt");

        BufferedReader bReader = new BufferedReader(reader);

        BufferedWriter bWriter = new BufferedWriter(writer);

        String temp = "";

        while((temp=bReader.readLine())!=null) {

            bWriter.write(temp);

        }

        bWriter.flush();

        bWriter.close();

        bReader.close();

    }

    private static void testFileInputStream() throws IOException {

        FileInputStream fis = new FileInputStream("/Users/qiaojiafei/Documents/zz.png");

        FileOutputStream fos = new FileOutputStream("/Users/qiaojiafei/Documents/zz_copy.png");

        BufferedInputStream bInputStream = new BufferedInputStream(fis);

        BufferedOutputStream bOutputStream = new BufferedOutputStream(fos);

        int temp = 0;

        while((temp=bInputStream.read()) != -1) {

            bOutputStream.write(temp);

        }

        bOutputStream.flush();

        bOutputStream.close();

        bInputStream.close();

    }

}