HFile
jhplot.io

Class HFile



  • public class HFileextends Object
    Write or read objects in sequential order using the Java serialization. The objects inside files are gzipped on-fly. The size of serialized files should be significantly smaller than when using HFile class. Use "close()" to flush buffered output stream. Use BrowserHFile to browser all entries in a GUI frame. Normally, files should have the extension ".jser". Files can be viewed using BrowserHFile.

    You can also insert objects using the keys and read them back. In this case, avoid writing many objects without the keys since the extraction of keys will be very inefficient. Try not mix write/read with keys or without.

    • Constructor Summary

      Constructors 
      Constructor and Description
      HFile(String file)
      Open file for reading objects from a serialized file in sequential order.
      HFile(String file, String option)
      Open file for reading objects from a serialized file in sequential order.
      HFile(String file, String option, boolean compression)
      Open a file to write/read objects to/from a serialized file in sequential order.
      HFile(String file, String option, boolean compression, int bufferSize)
      Open a file to write/read objects to/from a serialized file in sequential order.
    • Constructor Detail

      • HFile

        public HFile(String file,     String option,     boolean compression,     int bufferSize)
        Open a file to write/read objects to/from a serialized file in sequential order. Objects can be gzipped/gunzipped on-fly. If "w" option is set, the old file will be removed. Use close() to flash the buffer and close the file. You can set buffer size for I/O . Make it larger for a heavy I/O. It is best to use buffer sizes that are multiples of 1024 bytes. That works best with most built-in buffering in hard disks.

        You can also insert an object using a string key.

        If the file name starts from http or ftp, we assume it is located on the Web and will attempt to read it from URL.

        Parameters:
        file - File name. Can be located on URL if starts from http or ftp.
        option - Option to create the file. If "w" - write a file (or read) file, if "r" only read created file.
        compression - if true, objects are compressed on-fly using GZIP
        bufferSize - set buffer size for I/O. It is best to use buffer sizes that are multiples of 1024 bytes.
      • HFile

        public HFile(String file,     String option,     boolean compression)
        Open a file to write/read objects to/from a serialized file in sequential order. Objects can be gzipped/gunzipped on-fly. If "w" option is set, the old file will be removed. Use close() to flash the buffer and close the file. The default buffer size is 12 k (i.e. 12 * 1024).
        Parameters:
        file - File name
        option - Option to create the file. If "w" - write a file (or read) file, if "r" only read created file.
        compression - if true, objects are compressed on-fly using GZIP
        buffer - set buffer size for I/O. It is best to use buffer sizes that are multiples of 1024 bytes.
      • HFile

        public HFile(String file)
        Open file for reading objects from a serialized file in sequential order. By default, entries are compressed.
        Parameters:
        file - File name
      • HFile

        public HFile(String file,     String option)
        Open file for reading objects from a serialized file in sequential order. By default, objects are compressed.
        Parameters:
        file - File name
        option - Option to create the file. If "w" - write a file (or read) file, if "r" only read created file.
    • Method Detail

      • getBufferSize

        public int getBufferSize()
        Get current buffer size for I/O.
      • write

        public boolean write(String key,            Object ob)
        Add an object using a key.
        Parameters:
        key - key to access the object.
        ob - object to be inserted.
        Returns:
        false if the key exits.
      • write

        public boolean write(Object ob)
        Add an object to a file
        Parameters:
        ob - Object
        key - key for object
        Returns:
        true if success
      • setFlush

        public void setFlush(int reset)
        Set after how many events data will be flushed. The stream will flush all the objects from the identity hash table. The default is 100.
        Parameters:
        reset - after how many events data will be reset.
      • getObjectMap

        public Map<String,Object> getObjectMap()
        Return objects stored in the form of a map.
        Returns:
      • getEntries

        public int getEntries()
        Return processed number of entries. Entries with the key not counted.
        Returns:
        No of processed events
      • read

        public Object read()
        Get object from a file. Return Null if the end if file is reached.
        Returns:
        Object extracted object (or Null)
      • read

        public Object read(String key)
        Read an object using a key if exits.
        Parameters:
        key -
        Returns:
        returned object.
      • close

        public boolean close()
        Close the file
        Returns:
      • doc

        public void doc()
        Show online documentation.

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