Package java.io

Class BufferedReader

  • All Implemented Interfaces:
    Closeable, AutoCloseable, Readable
    Direct Known Subclasses:
    LineNumberReader, PemReader
    public class BufferedReader
extends Reader
    Wraps an existing Reader and buffers the input. Expensive interaction with the underlying reader is minimized, since most (smaller) requests can be satisfied by accessing the buffer alone. The drawback is that some extra space is required to hold the buffer and that copying takes place when filling that buffer, but this is usually outweighed by the performance benefits.

    A typical application pattern for the class looks like this:

     BufferedReader buf = new BufferedReader(new FileReader("file.java"));
    Since:
    1.1
    See Also:
    BufferedWriter

    • Field Summary

    • Constructor Summary

      Constructors 
      Constructor Description
      BufferedReader​(Reader in)
      Constructs a new BufferedReader, providing in with a buffer of 8192 characters.
      BufferedReader​(Reader in, int size)
      Constructs a new BufferedReader, providing in with size characters of buffer.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void close()
      Closes this reader.
      void mark​(int markLimit)
      Sets a mark position in this reader.
      boolean markSupported()
      Indicates whether this reader supports the mark() and reset() methods.
      int read()
      Reads a single character from this reader and returns it with the two higher-order bytes set to 0.
      int read​(char[] buffer, int offset, int length)
      Reads up to length characters from this reader and stores them at offset in the character array buffer.
      String readLine()
      Returns the next line of text available from this reader.
      boolean ready()
      Indicates whether this reader is ready to be read without blocking.
      void reset()
      Resets this reader's position to the last mark() location.
      long skip​(long charCount)
      Skips at most charCount chars in this stream.

    • Constructor Detail

      • BufferedReader

        public BufferedReader​(Reader in)
        Constructs a new BufferedReader, providing in with a buffer of 8192 characters.
        Parameters:
        in - the Reader the buffer reads from.

      • BufferedReader

        public BufferedReader​(Reader in,
                      int size)
        Constructs a new BufferedReader, providing in with size characters of buffer.
        Parameters:
        in - the InputStream the buffer reads from.
        size - the size of buffer in characters.
        Throws:
        IllegalArgumentException - if size <= 0.

    • Method Detail

      • close

        public void close()
           throws IOException
        Closes this reader. This implementation closes the buffered source reader and releases the buffer. Nothing is done if this reader has already been closed.
        Specified by:
        close in interface AutoCloseable
        Specified by:
        close in interface Closeable
        Specified by:
        close in class Reader
        Throws:
        IOException - if an error occurs while closing this reader.

      • mark

        public void mark​(int markLimit)
          throws IOException
        Sets a mark position in this reader. The parameter markLimit indicates how many characters can be read before the mark is invalidated. Calling reset() will reposition the reader back to the marked position if markLimit has not been surpassed.
        Overrides:
        mark in class Reader
        Parameters:
        markLimit - the number of characters that can be read before the mark is invalidated.
        Throws:
        IllegalArgumentException - if markLimit < 0.
        IOException - if an error occurs while setting a mark in this reader.
        See Also:
        markSupported(), reset()

      • markSupported

        public boolean markSupported()
        Indicates whether this reader supports the mark() and reset() methods. This implementation returns true.
        Overrides:
        markSupported in class Reader
        Returns:
        true for BufferedReader.
        See Also:
        mark(int), reset()

      • read

        public int read()
         throws IOException
        Reads a single character from this reader and returns it with the two higher-order bytes set to 0. If possible, BufferedReader returns a character from the buffer. If there are no characters available in the buffer, it fills the buffer and then returns a character. It returns -1 if there are no more characters in the source reader.
        Overrides:
        read in class Reader
        Returns:
        the character read or -1 if the end of the source reader has been reached.
        Throws:
        IOException - if this reader is closed or some other I/O error occurs.

      • read

        public int read​(char[] buffer,
                int offset,
                int length)
         throws IOException
        Reads up to length characters from this reader and stores them at offset in the character array buffer. Returns the number of characters actually read or -1 if the end of the source reader has been reached. If all the buffered characters have been used, a mark has not been set and the requested number of characters is larger than this readers buffer size, BufferedReader bypasses the buffer and simply places the results directly into buffer.
        Specified by:
        read in class Reader
        Throws:
        IndexOutOfBoundsException - if offset < 0 || length < 0 || offset + length > buffer.length.
        IOException - if this reader is closed or some other I/O error occurs.

      • readLine

        public String readLine()
                throws IOException
        Returns the next line of text available from this reader. A line is represented by zero or more characters followed by '\n', '\r', "\r\n" or the end of the reader. The string does not include the newline sequence.
        Returns:
        the contents of the line or null if no characters were read before the end of the reader has been reached.
        Throws:
        IOException - if this reader is closed or some other I/O error occurs.

      • ready

        public boolean ready()
              throws IOException
        Indicates whether this reader is ready to be read without blocking.
        Overrides:
        ready in class Reader
        Returns:
        true if this reader will not block when read is called, false if unknown or blocking will occur.
        Throws:
        IOException - if this reader is closed or some other I/O error occurs.
        See Also:
        read(), read(char[], int, int), readLine()

      • reset

        public void reset()
           throws IOException
        Resets this reader's position to the last mark() location. Invocations of read() and skip() will occur from this new location.
        Overrides:
        reset in class Reader
        Throws:
        IOException - if this reader is closed or no mark has been set.
        See Also:
        mark(int), markSupported()