Java Java类

BufferedInputStream 向另一个输入流添加了功能，即缓冲输入并支持标记和重置方法的能力。创建 BufferedInputStream 时，会创建一个内部缓冲区数组。当流中的字节被读取或跳过时，内部缓冲区会根据需要从包含的输入流中重新填充，一次很多字节。

构造函数和描述

• BufferedInputStream(InputStream in) ：创建一个 BufferedInputStream 并保存其参数，即输入流 in，以供以后使用。
• BufferedInputStream(InputStream in, int size) ：创建具有指定缓冲区大小的 BufferedInputStream，并保存其参数，即输入流 in，以备后用。

方法：

• int available() ：返回估计的字节数
  可以从此输入流中读取（或跳过）而无需
  通过下一次为此输入流调用方法而阻塞。

  Syntax:public int available()
                throws IOException
  Returns:
  an estimate of the number of bytes that can be 
  read (or skipped over) from this input stream without blocking.
  Throws:
  IOException
  

• void close() ：关闭此输入流并释放与该流关联的所有系统资源。

  Syntax:public void close()
             throws IOException
  Overrides:
  close in class FilterInputStream
  Throws:
  IOException 
  

• void mark(int readlimit) ：标记此输入流中的当前位置。

  Syntax:public void mark(int readlimit)
  Overrides:
  mark in class FilterInputStream
  Parameters:
  readlimit - the maximum limit of bytes that can be read 
  before the mark position becomes invalid.
  

• boolean markSupported() ：测试此输入流是否支持 mark 和 reset 方法。

  Syntax:public boolean markSupported()
  Overrides:
  markSupported in class FilterInputStream
  Returns:
  a boolean indicating if this stream type supports the mark and reset methods.
  

• int read() ：从输入流中读取数据的下一个字节。

  Syntax:public int read()
           throws IOException
  Returns:
  the next byte of data, or -1 if the end of the stream is reached.
  Throws:
  IOException 
  

• int read(byte[] b, int off, int len) ：从给定的偏移量开始，将此字节输入流中的字节读取到指定的字节数组中。

  Syntax:public int read(byte[] b,
         int off,
         int len)
           throws IOException
  Parameters:
  b - destination buffer.
  off - offset at which to start storing bytes.
  len - maximum number of bytes to read.
  Returns:
  the number of bytes read, or -1 if the end of the stream has been reached.
  Throws:
  IOException 
  

• void reset() ：将此流重新定位到最后一次在此输入流上调用标记方法时的位置。

  Syntax:public void reset()
             throws IOException
  Overrides:
  reset in class FilterInputStream
  Throws:
  IOException
  

• long skip(long n) ：跳过并丢弃此输入流中的 n 字节数据

  Syntax:public long skip(long n)
            throws IOException
  Parameters:
  n - the number of bytes to be skipped.
  Returns:
  the actual number of bytes skipped.
  Throws:
  IOException

程序：

// Java program to demonstrate working of BufferedInputStream
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
  
// Java program to demonstrate BufferedInputStream methods
class BufferedInputStreamDemo
{
    public static void main(String args[]) throws IOException
    {
        // attach the file to FileInputStream
        FileInputStream fin = new FileInputStream("file1.txt");
  
        BufferedInputStream bin = new BufferedInputStream(fin);
  
        // illustrating available method
        System.out.println("Number of remaining bytes:" +
                                            bin.available());
  
        // illustrating markSupported() and mark() method
        boolean b=bin.markSupported();
        if (b)
            bin.mark(bin.available());
  
        // illustrating skip method
        /*Original File content:
        * This is my first line
        * This is my second line*/
        bin.skip(4);
        System.out.println("FileContents :");
  
        // read characters from FileInputStream and
        // write them
        int ch;
        while ((ch=bin.read()) != -1)
            System.out.print((char)ch);
  
        // illustrating reset() method
        bin.reset();
        while ((ch=bin.read()) != -1)
            System.out.print((char)ch);
  
        // close the file
        fin.close();
    }
}

输出：

Number of remaining bytes:47
FileContents :
 is my first line
This is my second line
This is my first line
This is my second line

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