Java.io.StringReader class in Java

This a character stream class whose source is a string.
Constructor:

  • StringReader(String s) : Creates a new string reader.
  • Methods :

    • void close() : Closes the stream and releases any system resources associated with it.Once the stream has been closed, further read(), ready(), mark(), or reset() invocations will throw an IOException. Closing a previously closed stream has no effect.
      Syntax :public void close()
      
    • void mark(int readAheadLimit) : Marks the present position in the stream. Subsequent calls to reset() will reposition the stream to this point.
      Syntax :public void mark(int readAheadLimit)
                throws IOException
      Parameters:
      readAheadLimit - Limit on the number of characters that may 
      be read while still preserving the mark. Because the stream's input 
      comes from a string, there is no actual limit, so this argument 
      must not be negative, but is otherwise ignored.
      Throws:
      IllegalArgumentException
      IOException
    • boolean markSupported() : Tells whether this stream supports the mark() operation, which it does.
      Syntax :public boolean markSupported()
      Returns:
      true if and only if this stream supports the mark operation.
    • int read() : Reads a single character.
      Syntax :public int read()
               throws IOException
      Returns:
      The character read, or -1 if the end of the stream has been reached
      Throws:
      IOException
    • int read(char[] cbuf, int off, int len) : Reads characters into a portion of an array.
      Syntax :public int read(char[] cbuf,
             int off,
             int len)
               throws IOException
      Parameters:
      cbuf - Destination buffer
      off - Offset at which to start writing characters
      len - Maximum number of characters to read
      Returns:
      The number of characters read, or -1 if the end of the stream has been reached
      Throws:
      IOException
    • boolean ready() : Tells whether this stream is ready to be read.
      Syntax :public boolean ready()
                    throws IOException
      Returns:
      True if the next read() is guaranteed not to block for input
      Throws:
      IOException
    • void reset() : Resets the stream to the most recent mark, or to the beginning of the string if it has never been marked.
      Syntax :public void reset()
                 throws IOException
      Throws:
      IOException 
    • long skip(long ns) : Skips the specified number of characters in the stream.. Returns the number of characters that were skipped.
      The ns parameter may be negative, even though the skip method of the Reader superclass throws an exception in this case. Negative values of ns cause the stream to skip backwards. Negative return values indicate a skip backwards. It is not possible to skip backwards past the beginning of the string.



      If the entire string has been read or skipped, then this method has no effect and always returns 0.

      Syntax :public long skip(long ns)
                throws IOException
      Parameters:
      ns - The number of characters to skip
      Returns:
      The number of characters actually skipped
      Throws:
      IOException

    Program :

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    code

    //Java program demonstrating StringReader methods
    import java.io.IOException;
    import java.io.StringReader;
    class StringReaderDemo
    {
        public static void main(String[] args) throws IOException
        {
            StringReader str = new StringReader("GeeksforGeeks");
            char c[]=new char[7];
      
            //illustrating markSupported()
            if(str.markSupported())
            {
                System.out.println("Mark method is supported");
                // illustrating mark()
                str.mark(100);
            }
              
            //illustrating skip() method
            str.skip(5);
              
            //whether this stream is ready to be read.
            if(str.ready())
            {
                //illustrating read() method
                System.out.print((char)str.read());
                  
                //illustrating read(char cff[],int off,int len)
                str.read(c);
                for (int i = 0; i <7 ; i++) 
                {
                    System.out.print(c[i]);
                }
            }
              
            //illustrating reset() method
            str.reset();
              
            for (int i = 0; i < 5; i++) 
            {
                System.out.print((char)str.read());
            }
              
            //illustrating close()
            str.close();
        }
    }

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    Output :

    Mark method is supported
    forGeeksGeeks

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