关于java:字节流-字节缓冲流

字节缓冲流

BufferedOutputStream能够向底层输入流写入字节，底层调用次数缩小

默认封装大小都是8192

构造方法

//创立字节输入流对象
FileOutputStream fos = new FileOutputStream(name:"myByteStream\\bos.txt");//alt enter抛出异样 IOException
//字节缓冲输入流对象
BufferedOutputStream bos = new BufferedOutputStream(fos);

//下面两行等效代替
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(name:"myByteStream\\bos.txt"));

//写数据 靠底层的输入流去做 创立字节输入流对象
bos.write("hello\r\n".getBytes());
bos.write("world\r\n".getBytes());
//开释资源
bos.close();


//读数据 靠底层的输出流去做 创立字节输出流对象
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(name:"myByteStream\\bos.txt"));

//读数据 一次读取一个字节数据
int by;
while((by = bis.read())!=-1){
    sout((char)by);
}

//读数据 一次读取一个字节数组数据
byte[] bys = new byte[1024];
int len;
while((len = bis.read(bys))!=-1){
    sout(new String(bys,offset:0,len));
}
//开释资源
bis.close();

案例 复制视频

把”E:\itcast\字节流复制图片.avi”复制到模块目录下的”字节流复制图片.avi”

//记录开始工夫
long startTime = System.currentTimeMillis();

//复制视频
method1();//64565毫秒
method2();//107毫秒
method3();//405毫秒
method4();//60毫秒


//记录完结工夫
long endTime = System.currentTimeMillis();
sout("共耗时："+(endTime-startTime)+"毫秒");

//根本字节流一次读取一个字节
public static void method1(){
    //数据源
    FileInputStream fis = new FileInputStream(name:"E:\\itcast\\字节流复制图片.avi");
    //目的地
    FileOutputStream fos = new FileOutputStream(name:"myByteStream\\字节流复制图片.avi");
    int by;
    while((by = fis.read())!=-1){
    fos.write(by);
    }
fos.close();
fis.close();
}

//根本字节流一次读取一个字节数组
public static void method2(){
    //数据源
    FileInputStream fis = new FileInputStream(name:"E:\\itcast\\字节流复制图片.avi");
    //目的地
    FileOutputStream fos = new FileOutputStream(name:"myByteStream\\字节流复制图片.avi");
    byte[] bys = new byte[1024];
    int len;
    while((len = fis.read(bys))!=-1){
    fos.write(bys,offset:0,len));
    }
fos.close();
fis.close();
}

//字节缓冲流一次读取一个字节
public static void method3(){
    //数据源
    BufferedInputStream bis = new BufferedInputStream(new FileInputStream(name:"E:\\itcast\\字节流复制图片.avi"));
    //目的地
    BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(name:"myByteStream\\字节流复制图片.avi"));
    int by;
    while((by = bis.read())!=-1){
    bos.write(by);
    }
bos.close();
bis.close();
}

//字节缓冲流一次读取一个字节数组
public static void method3(){
    //数据源
    BufferedInputStream bis = new BufferedInputStream(new FileInputStream(name:"E:\\itcast\\字节流复制图片.avi"));
    //目的地
    BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(name:"myByteStream\\字节流复制图片.avi"));
    byte[] bys = new byte[1024];
    int len;
    while((len = bis.read(bys))!=-1){
    bos.write(bys,offset:0,len));
    }
bos.close();
bis.close();
}