java基础：IO流之缓冲流

简介

缓冲流属于处理流的一种

缓冲流有四种：BufferedInputStream、BufferedOutputStream、BufferedReader、BufferedWriter

缓冲流可以提高文件读写的速度

BufferedInputStream和BufferedOutputStream

先使用非缓冲流测试复制1个G的文件

File src = new File("C:\Users\wj\Desktop\01.ts");
File dest = new File("C:\Users\wj\Desktop\01.1.ts");
long start = System.currentTimeMillis();
try(FileInputStream fis = new FileInputStream(src);
    FileOutputStream fos = new FileOutputStream(dest)){
    byte[] buffer = new byte[1024];
    int len;
    while ((len = fis.read(buffer)) != -1){
        fos.write(buffer, 0, len);
    }
}catch (IOException e){
    e.printStackTrace();
}
long end = System.currentTimeMillis();
System.out.println(end-start);

耗费11s

BufferedInputStream和BufferedOutputStream的使用与FileInputStream和FileOutputStream差不多，这里不详细介绍。

这里jdk底层使用的装饰器设计模式，我们用BufferedInputStream包装FileInputStream即可，BufferedOutputStream也是如此。

File src = new File("C:\Users\wj\Desktop\01.ts");
File dest = new File("C:\Users\wj\Desktop\01.2.ts");
long start = System.currentTimeMillis();
try(BufferedInputStream bis = new BufferedInputStream(new FileInputStream(src));
    BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(dest))){
    byte[] buffer = new byte[1024];
    int len;
    while ((len = bis.read(buffer)) != -1){
        bos.write(buffer, 0, len);
    }
}catch (IOException e){
    e.printStackTrace();
}
long end = System.currentTimeMillis();
System.out.println(end-start);

两秒多就可以完成：效率提升十分明显

内部原理:内部提供了一个缓存区

BufferedReader、BufferedWriter

测试按行读取并复制文本文件：

File src = new File("斗破苍穹.txt");
File dest = new File("斗破苍穹-buffered.txt");
long start = System.currentTimeMillis();
try(BufferedReader br = new BufferedReader(new FileReader(src));
    BufferedWriter bw = new BufferedWriter(new FileWriter(dest))){
    String line ;
    //按行读取
    while ((line = br.readLine()) != null){
        bw.write(line);
        bw.newLine();//换行
    }
}catch (IOException e){
    e.printStackTrace();
}
long end = System.currentTimeMillis();
System.out.println(end-start);

复制出来的文件也是没有问题的