Java Java.io.SequenceInputStream用法及代碼示例

SequenceInputStream 類允許您連接多個InputStream。它一一讀取流的數據。它從輸入流的有序集合開始，從第一個輸入流讀取，直到到達文件末尾，然後從第二個輸入流讀取，依此類推，直到最後一個包含的輸入流到達文件末尾。

構造函數和說明

• 序列輸入流(枚舉e)：初始化一個新創建的SequenceInputStream，它必須是一個生成類型為InputStream的對象的Enumeration。
• 序列輸入流(輸入流 s1，InputStream s2)：通過記住兩個參數來初始化新創建的SequenceInputStream，這兩個參數將按順序讀取，首先是 s1，然後是 s2。

重要方法：

• read :從此輸入流讀取下一個數據字節。

  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.
  

• 讀取(字節[] b，int關閉，int長度)：從此輸入流中讀取最多 len 個字節的數據到數組中

  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 :返回可以從當前基礎輸入流中讀取(或跳過)的字節數的估計值，而不會被當前基礎輸入流的方法的下一次調用所阻塞。

  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:關閉此輸入流並釋放與該流關聯的所有係統資源。

  Syntax :
  public void close()
             throws IOException
  Overrides: close in class InputStream
  Throws:
  IOException - if an I/O error occurs.

以下是 SequenceInputStream 類的示例，它實現了一些重要的方法。
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(); 
    } 
} 

輸出：

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

注意：該程序不會在在線 IDE 上運行，因為沒有與其關聯的文件。