Java Java.io.PipedReader用法及代碼示例

這個類本質上是一個管道character-input流。在I/O中管道式，簡單來說就是JVM中同時運行的兩個線程之間的鏈接。因此，管道既可以用作源也可以用作目標。
如果向連接的管道輸出流提供數據字節的線程不再活動，則稱管道已損壞。

聲明：

public class PipedReader
  extends Reader

構造函數：

• PipedReader():創建一個PipedReader()，表明它未連接。
• PipedReader(int pSize)：創建一個 PipedReader，它未與指定的管道大小連接。
• PipedReader(PipedWriterStream src)：創建一個 PipedReader，它連接到 PipedWriterStream - ‘src’。
• PipedReader(PipedWriterStream src，int pSize)：創建一個連接到具有指定管道大小的管道寫入器的管道讀取器。

方法：

• read():java.io.PipedReader.read()從 PipedReader 讀取下一個字符。此方法會阻塞，直到字符可用為止。如果檢測到流結束，或者拋出異常且方法阻塞，則返回 -1
  Syntax():

  public int read()
  Parameters: 
  -----------
  Return :
  reads the next character from PipedReader.
  else, return-1 if end of the stream is detected.
  Exception : 
  -> IOException : if in case an IO error occurs.
  

  執行：

  
  // Java program illustrating the working of read() method 
    
  import java.io.*; 
  public class NewClass 
  { 
      public static void main(String[] args) throws IOException 
      { 
          PipedReader geek_reader = new PipedReader(); 
          PipedWriter geek_writer = new PipedWriter(); 
            
              geek_reader.connect(geek_writer); 
    
              // Use of read() method  
              geek_writer.write(71); 
              System.out.println("using read() : " + (char)geek_reader.read()); 
              geek_writer.write(69); 
              System.out.println("using read() : " + (char)geek_reader.read()); 
              geek_writer.write(75); 
              System.out.println("using read() : " + (char)geek_reader.read());         
      } 
  } 

  輸出：

  using read() : G
  using read() : E
  using read() : K

• 讀取(char[] carray，int 偏移量，int maxlen)：java.io.PipedReader.read(char[] carray, int 偏移量, int maxlen)從 PipedReader 流讀取最多 maxlen 個字符到字符數組。如果到達 Stream 末尾或引發異常，該方法將阻塞。
  Syntax :

  public int read(char[] carray, int offset, int maxlen)
  Parameters : 
  carray : buffer into which the data is to be read
  offset : starting in the destination array - 'carray'.
  maxlen : maximum length of array to be read
  Return :                                               
  next 'maxlen' bytes of the data as an integer value 
  return -1 is end of stream is reached
  Exception :
  -> IOException : if in case IO error occurs.
  

• close():java.io.PipedPipedReader.close()關閉 PipedReader Stream 並釋放分配的資源。
  Syntax :

  public void close()
  Parameters : 
  --------------
  Return :                                               
  void
  Exception :
  -> IOException : if in case IO error occurs.

• 連接(PipedWriter 源)：java.io.PipedReader.connect(PipedWriter源)將 PipedReader 連接到 ‘source’ 管道寫入器，如果 ‘source’ 是帶有其他流的管道，則會引發 IO 異常
  Syntax :

  public void connect(PipedWriter source)
  Parameters : 
  source : the PipedWriter to be connected to
  Return :                                               
  void
  Exception :
  -> IOException : if in case IO error occurs.

• ready():java.io.PipedPipedReader.ready()告知流是否已準備好讀取
  Syntax :

  public boolean ready()
  Parameters : 
  --------------
  Return :                                               
  true : if the stream is ready to be read else, false
  Exception :
  -> IOException : if in case IO error occurs.

  Java 程序說明了 PipedReader 類方法的用法原理：

  
  // Java program illustrating the working of PipedReader 
  // connect(), read(char[] carray, int offset, int maxlen), 
  // close(), ready() 
    
  import java.io.*; 
  public class NewClass 
  { 
      public static void main(String[] args) throws IOException 
      { 
          PipedReader geek_reader = new PipedReader(); 
          PipedWriter geek_writer = new PipedWriter(); 
    
          // Use of connect() : connecting geek_reader with geek_writer 
          geek_reader.connect(geek_writer); 
    
          geek_writer.write(71); 
          geek_writer.write(69); 
          geek_writer.write(69); 
          geek_writer.write(75); 
          geek_writer.write(83); 
    
          // Use of ready() method 
          System.out.print("Stream is ready to be read : "+geek_reader.ready()); 
    
          // Use of read(char[] carray, int offset, int maxlen) 
          System.out.print("\nUse of read(carray, offset, maxlen) : "); 
          char[] carray = new char[5]; 
          geek_reader.read(carray, 0, 5); 
    
          for (int i = 0; i < 5; i++) 
          { 
              System.out.print(carray[i]); 
          } 
    
          // USe of close() method : 
          System.out.println("\nClosing the stream"); 
          geek_reader.close(); 
      } 
  } 

  輸出：

  Stream is ready to be read : true
  Use of read(carray, offset, maxlen) : GEEKS
  Closing the stream

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