字节缓冲流(BufferedInputStream BufferedOutputSteam)

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1 . 提供了缓存区,提高了效率
2 . 缓冲流不直接与数据源打交道,与流打交道,则缓冲流为过滤流,或者处理流.
3 . 缓冲字节输入流,就是处理字节输入流的.要记住

BufferedInputStream bis =  null;            //注意 new 的时候bis = new BufferedInputStream(new FileInputStream(new File("abc.txt")));

package com.qf.demo2;import java.io.BufferedInputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.util.Arrays;/** * FileInputStream * FileOutputStream * FileReader * FileWriter *  * 都是文件流, 节点流 ,  *  *  *  过滤流(处理流) *缓冲流 *BufferedInputStream *BufferedOutputSteam *BufferedReader *BufferedWriter * * 字节     1024b -->1 kb *      1024kb --> 1 Mb *      1024Mb --> 1G *      1024G  --> 1T *在内存中提供了 一个  8kb 的缓冲区, 提高了  执行效率 * * * */public class Test {    public static void main(String[] args) {        BufferedInputStream bis =  null;        try {            //注意 new 的时候            bis = new BufferedInputStream(new FileInputStream(new File("abc.txt")));            byte[] bs= new byte[1024];            //读的数据放进bs数组里面            int num = bis.read(bs);            int num2 = bis.read(bs);            System.out.println(num2);            System.out.println(Arrays.toString(bs));                bis.read();            bis.read(bs, 0, 4);             } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally {            if(bis!=null){                try {                    bis.close();                } catch (IOException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }        }    }}

4 . 缓冲字节输出流,就是处理字节输出流的.要记住
5 . 将字符串转化为byte数组

"abcdef".getBytes()

BufferedOutputStream bos = null;bos = new BufferedOutputStream(new FileOutputStream(new File("ww.txt")));

package com.qf.demo2;import java.io.BufferedOutputStream;import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;public class Test2 {    public static void main(String[] args) {        BufferedOutputStream bos = null;        try {            bos = new BufferedOutputStream(new FileOutputStream(new File("ww.txt")));            bos.write(new byte[]{100,97,98,99});            bos.write(101);            bos.write("abcdef".getBytes(), 2, 4);            bos.flush();        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally {            if(bos!=null){                try {                    bos.close();                } catch (IOException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }        }    }}

6 . 文件字节流,读取数据的时候,会读出来对应的byte类型.
反过来,如果想利用文件输出流写入数据的时候,直接写数组,它会自动转换成对应的类型.比如,write(97) 则在文本中显示的是a.

7 . 需求
用文件流复制文件 ,计算耗时
用缓冲流复制同样的文件 ,计算耗时
来证明用缓冲流操作字节流会比字节流单独处理数据要速度快.
获取系统运行当前

long item2 = System.currentTimeMillis();

package com.qf.demo2;import java.io.BufferedInputStream;import java.io.BufferedOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;/** * 1 用文件流 复制文件 计算  耗时 * 2 用缓冲流 复制同样的文件  计算耗时 *  * @author Administrator * */public class Test3 {    public static void main(String[] args) {        String string = "C:\\Users\\Administrator\\Desktop\\第十七天\\第十七天视频\\第十七天上午.wmv";        File file = new File(string);        fileCopy(file);        bufferedCopy(file);    }    public static void  fileCopy(File file){        long time = System.currentTimeMillis();        FileInputStream fis =null;        FileOutputStream fos =null;        try {             fis = new FileInputStream(file);             fos = new FileOutputStream(new File("D:\\shipin.wmv"));            // 2 读            byte[] bs = new  byte[1024];            int num =0;            while((num = fis.read(bs))!=-1){                fos.write(bs, 0, num);                fos.flush();            }            long time2 = System.currentTimeMillis();            System.out.println("文件流复制完成,耗时"+(time2-time));        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally {            if(fis!=null){                try {                    fis.close();                } catch (IOException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }            if(fos!=null){                try {                    fos.close();                } catch (IOException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }        }    }    public static void bufferedCopy(File file){        BufferedInputStream bis = null;        BufferedOutputStream bos =  null;        long time = System.currentTimeMillis();        try {             bis = new BufferedInputStream(new FileInputStream(file));             bos = new BufferedOutputStream(new FileOutputStream(new File("D:\\aaa.wmv")));            byte[] bs = new byte[1024];            int num = 0;            while((num = bis.read(bs))!=-1){                bos.write(bs, 0, num);                bos.flush();            }            long item2 = System.currentTimeMillis();            System.out.println("缓冲流 复制完毕,"+(item2-time));        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally {            if(bis!=null){                try {                    bis.close();                } catch (IOException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }            if(bos!=null){                try {                    bos.close();                } catch (IOException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }        }    }}

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