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<a href="http://www.bruceeckel.com/javabook.html">Bruce Eckel's Thinking in Java</a>
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<a href="tij_c.html">Contents</a> | <a href="tij0107.html">Prev</a> | <a href="tij0109.html">Next</a>
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<H2 ALIGN=LEFT>
Input
and output
</H2>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">The
Java library classes for IO are divided by <A NAME="Index987"></A>input
and <A NAME="Index988"></A>output,
as you can see by looking at the online Java class hierarchy with your Web
browser. By inheritance, all classes derived from <A NAME="Index989"></A><A NAME="Index990"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
have basic methods called <A NAME="Index991"></A><A NAME="Index992"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>read(&#160;)
</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">for
reading a single byte or array of bytes. Likewise, all classes derived from <A NAME="Index993"></A><A NAME="Index994"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>OutputStream
</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">have
basic methods called <A NAME="Index995"></A><A NAME="Index996"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>write(&#160;)
</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">for
writing a single byte or array of bytes. However, you won&#8217;t generally use
these methods; they exist so more sophisticated classes can use them as they
provide a more useful interface. Thus, you&#8217;ll rarely create your stream
object by using a single class, but instead will layer multiple objects
together to provide your desired functionality. The fact that you create more
than one object to create a single resulting stream is the primary reason that
Java&#8217;s stream library is confusing.
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">It&#8217;s
helpful to categorize the classes by their functionality. The library designers
started by deciding that all classes that had anything to do with input would
be inherited from 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
and all classes that were associated with output would be inherited from 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>OutputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">.
</FONT><a name="_Toc375545383"></a><a name="_Toc408018611"></a><P></DIV>
<A NAME="Heading305"></A><H3 ALIGN=LEFT>
Types
of InputStream
</H3>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">&#8217;s
job is to represent classes that produce input from different sources. These
sources can be (and each has an associated subclass of 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">):
</FONT><P></DIV>
<OL>
<LI><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">	An
array of bytes
</FONT><LI><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">	A
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>String</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
object
</FONT><LI><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">	A
file
</FONT><LI><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">	A
&#8220;pipe,&#8221; which works like a physical <A NAME="Index997"></A><A NAME="Index998"></A>pipe:
you put things in one end and they come out the other
</FONT><LI><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">	A
sequence of other streams, so you can collect them together into a single stream
</FONT><LI><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">	Other
sources, such as an Internet connection. (This will be discussed in a later
chapter.)
</FONT></OL><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">In
addition, the 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterInputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
is also a type of 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">,
to provide a base class for "decorator" classes that attach attributes or
useful interfaces to input streams. This is discussed later.
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Table
10-1. Types of InputStream
</B></FONT><P></DIV>
<DIV ALIGN=LEFT><TABLE BORDER>
<COLGROUP>
      <COL width="76">
      <COL width="90">
      <COL width="162">
</COLGROUP>
<TR VALIGN="TOP">
<TH WIDTH=76 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Class</FONT><P></DIV>
</TH>
<TH WIDTH=90 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Function</FONT><P></DIV>
</TH>
<TH WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Constructor
Arguments
</FONT><P></DIV>
</TH>
</TR>
<TR VALIGN="TOP">
<TH WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">How
to use it
</FONT><P></DIV>
</TH>
</TR>
<A NAME="Index999"></A><A NAME="Index1000"></A><TR VALIGN="TOP">
<TD WIDTH=76 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>ByteArray-InputStream</B></FONT><P></DIV>
</TD>
<TD WIDTH=90 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Allows
a buffer in memory to be used as an 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">.</FONT><P></DIV>
</TD>
<TD WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">The
buffer from which to extract the bytes.
</FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">As
a source of data. Connect it to a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterInputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
object to provide a useful interface.
</FONT><P></DIV>
</TD>
</TR>
<A NAME="Index1001"></A><A NAME="Index1002"></A><TR VALIGN="TOP">
<TD WIDTH=76 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>StringBuffer-InputStream</B></FONT><P></DIV>
</TD>
<TD WIDTH=90 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Converts
a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>String</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
into an 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">.</FONT><P></DIV>
</TD>
<TD WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">A
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>String</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">.
The underlying implementation actually uses a <A NAME="Index1003"></A><A NAME="Index1004"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>StringBuffer</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">.</FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">As
a source of data. Connect it to a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterInputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
object to provide a useful interface.
</FONT><P></DIV>
</TD>
</TR>
<A NAME="Index1005"></A><A NAME="Index1006"></A><TR VALIGN="TOP">
<TD WIDTH=76 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>File-InputStream</B></FONT><P></DIV>
</TD>
<TD WIDTH=90 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">For
reading information from a file.
</FONT><P></DIV>
</TD>
<TD WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">A
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>String</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
representing the file name, or a <A NAME="Index1007"></A><A NAME="Index1008"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>File</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
or <A NAME="Index1009"></A><A NAME="Index1010"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FileDescriptor</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
object.
</FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">As
a source of data. Connect it to a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterInputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
object to provide a useful interface.
</FONT><P></DIV>
</TD>
</TR>
</TABLE></DIV>
<DIV ALIGN=LEFT><P></DIV><DIV ALIGN=LEFT><A NAME="Index1011"></A><A NAME="Index1012"></A><P></DIV>
<DIV ALIGN=LEFT><TABLE BORDER>
<COLGROUP>
      <COL width="76">
      <COL width="90">
      <COL width="162">
</COLGROUP>
<TR VALIGN="TOP">
<TD WIDTH=76 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Piped-InputStream</B></FONT><P></DIV>
</TD>
<TD WIDTH=90 COLSPAN=1 ROWSPAN=2 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Produces
the data that&#8217;s being written to the associated <A NAME="Index1013"></A><A NAME="Index1014"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>PipedOutput-Stream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">.
Implements the &#8220;piping&#8221; concept.
</FONT><P></DIV>
</TD>
<TD WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>PipedOutputStream</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=162 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">As
a source of data in multithreading. Connect it to a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterInputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
object to provide a useful interface.
</FONT><P></DIV>
</TD>
</TR>
<A NAME="Index1015"></A><A NAME="Index1016"></A><TR VALIGN="TOP">
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