java缓冲区输入输出流，提高执行效率，拷贝文件

Posted 2022-11-25 weixin_ancenhw

//缓冲区输出流
public class FileStream 
    public static void main(String[] args) throws IOException 
//        定义要输出的文本路径
        FileOutputStream os = new FileOutputStream("03.txt");
//        定义缓冲区
        BufferedOutputStream outputStream = new BufferedOutputStream(os);
        outputStream.write("跟你一起去看".getBytes());
        
        
        outputStream.close();
        os.close();

    

//读取缓冲区输入流
//读取缓冲区输入流
public class FileStream 
    public static void main(String[] args) throws IOException 
        FileInputStream inputStream = new FileInputStream("03.txt");
        BufferedInputStream is = new BufferedInputStream(inputStream);
        int len=0;
        byte[] arrChar=new byte[1024];

        while ((len=is.read(arrChar))!=-1)
            //从0开始转换len定义个数
            System.out.print(new String(arrChar,0,len));
        
       //不需要关闭inputStream，is关闭后，会自带关闭不需要关闭inputStream
        is.close();


    

缓冲区拷贝文件执行效率的对比

public class CopyFile 
    //利用缓冲区实现文件的快速拷贝
    public static void main(String[] args) throws IOException 

        //method01();
        method02();

    

    private static void method02() throws IOException
        FileInputStream inputStream = new FileInputStream("C:\\\\Users\\\\Administrator\\\\Downloads\\\\本本之家二手交易平台设计与实现.rar");
        BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
        FileOutputStream outputStream = new FileOutputStream("bb.rar");
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
        byte[] bytes = new byte[1024];
        int len=0;
        long startTime = System.currentTimeMillis();
        while ((len=bufferedInputStream.read(bytes))!=-1)
            bufferedOutputStream.write(bytes);
        
        long endTime = System.currentTimeMillis();
        System.out.println(endTime-startTime);
        bufferedInputStream.close();
        bufferedOutputStream.close();

    


    public static void method01() throws IOException
        FileInputStream inputStream = new FileInputStream("C:\\\\Users\\\\Administrator\\\\Downloads\\\\本本之家二手交易平台设计与实现.rar");

        FileOutputStream outputStream = new FileOutputStream("aa.rar");
        byte[] arr=new byte[1024];
        int len=0;
        long startTime = System.currentTimeMillis();
        while ((len=inputStream.read(arr))!=-1)
            outputStream.write(arr);
        
        long endTime = System.currentTimeMillis();
        System.out.println(endTime-startTime);
        inputStream.close();
        outputStream.close();
    

缓冲区写入字符

    public static void main(String[] args) throws IOException 
        //字符缓冲写入
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("03.txt"));
        for (int i = 0; i < 10; i++) 
            bufferedWriter.write("hello word "+i);
            //换行
            bufferedWriter.newLine();
        
        bufferedWriter.close();
    

读取字符

    //读取字符
    public static void main(String[] args) throws IOException 
        //字符缓冲区读出数据
        BufferedReader rd = new BufferedReader(new FileReader("03.txt"));
        String line;
        while ((line=rd.readLine())!=null)
            System.out.println(line);
        
        rd.close();