Java IO frameworks

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Java I/O frameworks

• Input and output

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Java I/O overview

• 3 different frameworks
• Streams (Java 1.0)
• Readers and writers (Java 1.2)
• NIO New I/O (java 1.4)
• Some bridging between frameworks for backward
  compatibility
• Main concept decorators (wrappers)
• Followed through most of the frameworks

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Decorators

• Basic idea
• All classes implement the same basic
  functionality
• Concrete suppliers actually do something
• Decorators take instance of that interface as
  constructor parameter, and wrap it with extra
  functionality (decorate)

Each decoratortakes the previousone, use it,
and extends its functionality
Source
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Decorators class diagram
BaseFuncfunc()
Decorated object
Sourcefunc()
Decoratorfunc()
Actually do something
Use the decorated objectto do some more
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I/O decorators

• Basic function is reading or writing byte arrays
• Sources are actual I/O devices or sources, like
• Files
• Sockets
• Byte arrays
• Pipes
• Strings

• Decorating functions are
• Reading/writing primitive (int, char, float)
• Reading/writing objects
• Compressing / decompressing
• Buffering
• Reading lines of text
• Printing
• Writing lines
• Filtering

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Java steams

• The original Java I/O framework
• Located at the java.io package
• Basic operations are reading or writing ints and
  byte arrays InputStream and OutputStream
  abstract classes
• Sources/targets are mainly files, sockets, etc.
• Decorators include object handling, filtering,
  compression, (some) buffering, etc.
• Deprecated replaced with readers/writers

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Java readers/writers

• Javas replacement for old streams
• But also at the same package
• There are bridging classes InputStreamReader and
  OutputStreamWriter
• Many take streams as decorated objects
• Similar basic operations Reader and Writer
• Similar sources/targets files, sockets
• Similar decorators buffering, filtering,
  strings
• Slightly added and improved functionality

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Java New I/O - NIO

• New, innovative I/O framework
• Located at its own package java.nio
• Caused changes throughout the entire library
• Based on buffers and channels
• Like streams, but read in big chunks
• Used mainly for large-scale operations, like
• File mapping to memory
• Text charset decoding regular-expressions parsing
• Channels gathering and scattering

Neo