Java - Readers and Writers

Why Readers and Writers

Input and output streams are byte-based streams.

Readers and writers are character-based streams.

A reader reads character-based data from a data source. A writer writes character-based data to a data sink.

The following table lists Classes in Byte-based and Character-based Input Streams

Byte-based Input Stream Class Character-based Input Stream Class
InputStream Reader
ByteArrayInputStream CharArrayReader
StringBufferInputStream StringReader
PipedInputStream PipedReader
FileInputStream FileReader
No corresponding classInputStreamReader
FilterInputStream FilterReader
BufferedInputStream BufferedReader
PushbackInputStream PushbackReader
DataInputStream No corresponding class
ObjectInputStream No corresponding class

The following table compares Classes from Byte-based Output Streams and Character-based Output Streams

Byte-based Output Stream Class Character-based Output Stream Class
OutputStream Writer
No corresponding class StringWriter
FileOutputStream FileWriter
No corresponding class OutputStreamWriter
FilterOutputStream FilterWriter
BufferedOutputStream BufferedWriter
DataOutputStream No corresponding class
ObjectOutputStream No corresponding class
PrintStream PrintWriter

Use the InputStreamReader class if you have a stream that supplies bytes and you want to read characters by getting those bytes decoded into characters.

Create a Reader object from an InputStream object using the platform default encoding
Reader reader = new InputStreamReader(iso);

Create a Reader object from an InputStream using the "US-ASCII" encoding

Reader reader = new InputStreamReader(iso, "US-ASCII");

You can create a Writer object to spit out characters from a bytes-based output stream, assuming that oso is an OutputStream object:

Create a Writer object from OutputStream using the platform default encoding

Writer writer = new OutputStreamWriter(oso);

Create a Writer object from OutputStream using the "US-ASCII" encoding

Writer writer = new OutputStreamWriter(oso, "US-ASCII");

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