Java Java.io.BufferedInputStream用法及代码示例

BufferedInputStream 为另一个输入 stream-namely 添加了函数，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。当读取或跳过流中的字节时，内部缓冲区会根据需要从包含的输入流中重新填充，一次填充多个字节。

构造函数和说明

• BufferedInputStream(输入流中)：创建 BufferedInputStream 并保存其参数(输入流)以供以后使用。
• BufferedInputStream(输入流，int大小)：创建具有指定缓冲区大小的BufferedInputStream，并保存其参数(输入流)以供以后使用。

方法：

• int available()：返回字节数的估计值
  可以从此输入流中读取(或跳过)，而无需
  下次调用该输入流的方法时会阻塞。

  用法：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
  

• 无效close()：关闭此输入流并释放与该流关联的所有系统资源。

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

• 无效标记(int readlimit)：标记此输入流中的当前位置。

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

• 布尔值markSupported()：测试此输入流是否支持标记和重置方法。

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

• int read()：从输入流读取下一个数据字节。

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

• int 读取(字节[] b，int 关闭，int len)：从给定的偏移量开始，将此 byte-input 流中的字节读取到指定的字节数组中。

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

• 无效reset()：将此流重新定位到上次在此输入流上调用 mark 方法时的位置。

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

• 长跳过(长n)：跳过并丢弃此输入流中的 n 个字节的数据

  用法：public long skip(long n)
            throws IOException
  Parameters:
  n - the number of bytes to be skipped.
  返回：
  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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