Java Java.io.PipedReader用法及代码示例

这个类本质上是一个管道character-input流。在I/O中管道式，简单来说就是JVM中同时运行的两个线程之间的链接。因此，管道既可以用作源也可以用作目标。
如果向连接的管道输出流提供数据字节的线程不再活动，则称管道已损坏。

声明：

public class PipedReader
  extends Reader

构造函数：

• PipedReader():创建一个PipedReader()，表明它未连接。
• PipedReader(int pSize)：创建一个 PipedReader，它未与指定的管道大小连接。
• PipedReader(PipedWriterStream src)：创建一个 PipedReader，它连接到 PipedWriterStream - ‘src’。
• PipedReader(PipedWriterStream src，int pSize)：创建一个连接到具有指定管道大小的管道写入器的管道读取器。

方法：

• read():java.io.PipedReader.read()从 PipedReader 读取下一个字符。此方法会阻塞，直到字符可用为止。如果检测到流结束，或者抛出异常且方法阻塞，则返回 -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.
  

  执行：

  
  // 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());         
      } 
  } 

  输出：

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

• 读取(char[] carray，int 偏移量，int maxlen)：java.io.PipedReader.read(char[] carray, int 偏移量, int maxlen)从 PipedReader 流读取最多 maxlen 个字符到字符数组。如果到达 Stream 末尾或引发异常，该方法将阻塞。
  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()关闭 PipedReader Stream 并释放分配的资源。
  Syntax :

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

• 连接(PipedWriter 源)：java.io.PipedReader.connect(PipedWriter源)将 PipedReader 连接到 ‘source’ 管道写入器，如果 ‘source’ 是带有其他流的管道，则会引发 IO 异常
  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()告知流是否已准备好读取
  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 程序说明了 PipedReader 类方法的用法原理：

  
  // 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(); 
      } 
  } 

  输出：

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

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