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

SequenceInputStream 类允许您连接多个InputStream。它一一读取流的数据。它从输入流的有序集合开始，从第一个输入流读取，直到到达文件末尾，然后从第二个输入流读取，依此类推，直到最后一个包含的输入流到达文件末尾。

构造函数和说明

• 序列输入流(枚举e)：初始化一个新创建的SequenceInputStream，它必须是一个生成类型为InputStream的对象的Enumeration。
• 序列输入流(输入流 s1，InputStream s2)：通过记住两个参数来初始化新创建的SequenceInputStream，这两个参数将按顺序读取，首先是 s1，然后是 s2。

重要方法：

• read :从此输入流读取下一个数据字节。

  用法：
  public int read()
           throws IOException 
  返回： the next byte of data, or -1 if the end of the stream is reached.
  Throws: IOException - if an I/O error occurs.
  

• 读取(字节[] b，int关闭，int长度)：从此输入流中读取最多 len 个字节的数据到数组中

  用法：
  public int read(byte[] b,
         int off,
         int len)
           throws IOException
  Overrides: read in class InputStream
  Parameters:
  b - the buffer into which the data is read.
  off - the start offset in array b at which the data is written.
  len - the maximum number of bytes read.
  Returns: int the number of bytes read.
  Throws:
  NullPointerException - If b is null.
  IndexOutOfBoundsException - If off is negative, len is negative, 
  or len is greater than b.length - off
  IOException - if an I/O error occurs.

• available :返回可以从当前基础输入流中读取(或跳过)的字节数的估计值，而不会被当前基础输入流的方法的下一次调用所阻塞。

  Syntax :
  public int available()
                throws IOException 
  Overrides: available in class InputStream
  返回：an estimate of the number of bytes that can be read (or skipped over) 
  from the current underlying input stream without blocking or 0 if this input stream
  has been closed by invoking its close() method
  Throws:
  IOException - if an I/O error occurs.

• 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 InputStream
  Throws:
  IOException - if an I/O error occurs.

以下是 SequenceInputStream 类的示例，它实现了一些重要的方法。
程序：

//Java program to demonstrate SequenceInputStream 
import java.io.*; 
import java.util.*; 
  
class SequenceISDemp 
{ 
    public static void main(String args[])throws IOException 
    { 
  
        //creating the FileInputStream objects for all the following files 
        FileInputStream fin=new FileInputStream("file1.txt"); 
        FileInputStream fin2=new FileInputStream("file2.txt"); 
        FileInputStream fin3=new FileInputStream("file3.txt"); 
  
        //adding fileinputstream obj to a vector object 
        Vector v = new Vector(); 
          
        v.add(fin); 
        v.add(fin2); 
        v.add(fin3); 
          
        //creating enumeration object by calling the elements method 
        Enumeration enumeration = v.elements(); 
  
        //passing the enumeration object in the constructor 
        SequenceInputStream sin = new SequenceInputStream(enumeration); 
          
        // determine how many bytes are available in the first stream 
        System.out.println("" + sin.available()); 
          
        // Estimating the number of bytes that can be read  
        // from the current underlying input stream  
        System.out.println( sin.available()); 
          
        int i = 0; 
        while((i = sin.read())! = -1) 
        { 
            System.out.print((char)i); 
        } 
        sin.close(); 
        fin.close(); 
        fin2.close(); 
        fin3.close(); 
    } 
} 

输出：

19
This is first file This is second file This is third file

注意：该程序不会在在线 IDE 上运行，因为没有与其关联的文件。