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<td>
<a href="http://www.bruceeckel.com/javabook.html">Bruce Eckel's Thinking in Java</a>
</td>
<td align="right">
<a href="tij_c.html">Contents</a> | <a href="tij0113.html">Prev</a> | <a href="tij0115.html">Next</a>
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<H2 ALIGN=LEFT>
Java
1.1 IO streams
<P><A NAME="Index1181"></A></H2>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">At
this point you might be scratching your head, wondering if there is another
design for IO streams that could require 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><I>more</I></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
typing. Could someone have come up with an odder design?&#8221; Prepare
yourself: Java 1.1 makes some significant modifications to the IO stream
library. When you see the <A NAME="Index1182"></A><A NAME="Index1183"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Reader</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
and <A NAME="Index1184"></A><A NAME="Index1185"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Writer</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
classes your first thought (like mine) might be that these were meant to
replace the 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
and 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>OutputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
classes. But that&#8217;s not the case. Although some aspects of the original
streams library are deprecated (if you use them you will receive a warning from
the compiler), the old streams have been left in for backwards compatibility and:
</FONT><P></DIV>
<OL>
<LI><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">	New
classes have been put into the old hierarchy, so it&#8217;s obvious that Sun is
not abandoning the old streams.
</FONT><LI><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">	There
are times when you&#8217;re supposed to use classes in the old hierarchy 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><I>in
combination
</I></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
with classes in the new hierarchy and to accomplish this there are
&#8220;bridge&#8221; classes: <A NAME="Index1186"></A><A NAME="Index1187"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStreamReader</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
converts an 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream
</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">to
a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Reader
</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">and
<A NAME="Index1188"></A><A NAME="Index1189"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>OutputStreamWriter</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
converts an 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>OutputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
to a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Writer</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">.</FONT></OL><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">As
a result there are situations in which you have 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><I>more</I></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
layers of wrapping with the new IO stream library than with the old. Again,
this is a drawback of the decorator pattern &#8211; the price you pay for added
flexibility.
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">The
most important reason for adding the 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Reader</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
and 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Writer</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
hierarchies in Java 1.1<A NAME="Index1190"></A>
is for <A NAME="Index1191"></A><A NAME="Index1192"></A>internationalization.
The old IO stream hierarchy supports only 8-bit byte streams and doesn&#8217;t
handle the 16-bit Unicode characters well. Since Unicode is used for
internationalization (and Java&#8217;s native 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>char
</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">is
16-bit <A NAME="Index1193"></A><A NAME="Index1194"></A>Unicode),
the 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Reader</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
and 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Writer</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
hierarchies were added to support Unicode in all IO operations. In addition,
the new libraries are designed for faster operations than the old.
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">As
is the practice in this book, I will attempt to provide an overview of the
classes but assume that you will use online documentation to determine all the
details, such as the exhaustive list of methods.
</FONT><a name="_Toc408018629"></a><P></DIV>
<A NAME="Heading334"></A><H3 ALIGN=LEFT>
Sources
and sinks of data
</H3>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Almost
all of the Java 1.0<A NAME="Index1195"></A>
IO stream classes have corresponding Java 1.1<A NAME="Index1196"></A>
classes to provide native Unicode manipulation. It would be easiest to say
&#8220;Always use the new classes, never use the old ones,&#8221; but things
are not that simple. Sometimes you are forced into using the Java 1.0 IO stream
classes because of the library design; in particular, the 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>java.util.zip</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
libraries are new additions to the old stream library and they rely on old
stream components. So the most sensible approach to take is to 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><I>try</I></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
to use the 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Reader</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
and 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Writer</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
classes whenever you can, and you&#8217;ll discover the situations when you
have to drop back into the old libraries because your code won&#8217;t compile.
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Here
is a table that shows the correspondence between the sources and sinks of
information (that is, where the data physically comes from or goes to) in the
old and new libraries.
</FONT><P></DIV>
<DIV ALIGN=LEFT><TABLE BORDER>
<COLGROUP>
      <COL width="144">
      <COL width="175">
</COLGROUP>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Sources
&amp; Sinks:
</FONT><P><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Java
1.0<A NAME="Index1197"></A>
class
</FONT><P></DIV>
</TD>
<TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Corresponding
Java 1.1<A NAME="Index1198"></A>
class
</FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStream</B></FONT><P></DIV>
</TD>
<A NAME="Index1199"></A><A NAME="Index1200"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Reader</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
</FONT><P><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">converter:
<A NAME="Index1201"></A><A NAME="Index1202"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>InputStreamReader</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>OutputStream</B></FONT><P></DIV>
</TD>
<A NAME="Index1203"></A><A NAME="Index1204"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Writer</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
</FONT><P><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">converter:
<A NAME="Index1205"></A><A NAME="Index1206"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>OutputStreamWriter</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FileInputStream</B></FONT><P></DIV>
</TD>
<A NAME="Index1207"></A><A NAME="Index1208"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FileReader</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FileOutputStream</B></FONT><P></DIV>
</TD>
<A NAME="Index1209"></A><A NAME="Index1210"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FileWriter</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>StringBufferInputStream</B></FONT><P></DIV>
</TD>
<A NAME="Index1211"></A><A NAME="Index1212"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>StringReader</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">(no
corresponding class)
</FONT><P></DIV>
</TD>
<A NAME="Index1213"></A><A NAME="Index1214"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>StringWriter</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>ByteArrayInputStream</B></FONT><P></DIV>
</TD>
<A NAME="Index1215"></A><A NAME="Index1216"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>CharArrayReader</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>ByteArrayOutputStream</B></FONT><P></DIV>
</TD>
<A NAME="Index1217"></A><A NAME="Index1218"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>CharArrayWriter</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>PipedInputStream</B></FONT><P></DIV>
</TD>
<A NAME="Index1219"></A><A NAME="Index1220"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>PipedReader</B></FONT><P></DIV>
</TD>
</TR>
<TR VALIGN="TOP">
<TD WIDTH=144 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>
<A NAME="Index1221"></A><A NAME="Index1222"></A><TD WIDTH=175 COLSPAN=1 ROWSPAN=1 VALIGN=TOP>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>PipedWriter</B></FONT><P></DIV>
</TD>
</TR>
</TABLE></DIV>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">In
general, you&#8217;ll find that the interfaces in the old library components
and the new ones are similar if not identical.
</FONT><a name="_Toc408018630"></a><P></DIV>
<A NAME="Heading335"></A><H3 ALIGN=LEFT>
Modifying
stream behavior
</H3>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">In
Java 1.0<A NAME="Index1223"></A>,
streams were adapted for particular needs using &#8220;decorator&#8221;
subclasses of 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterInputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
and 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterOutputStream.</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
Java 1.1<A NAME="Index1224"></A>
IO streams continues the use of this idea, but the model of deriving all of the
decorators from the same &#8220;filter&#8221; base class is not followed. This
can make it a bit confusing if you&#8217;re trying to understand it by looking
at the class hierarchy.
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">In
the following table, the correspondence is a rougher approximation than in the
previous table. The difference is because of the class organization: while 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>BufferedOutputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
is a subclass of 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterOutputStream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">,
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>BufferedWriter</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
is 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><I>not</I></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
a subclass of 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>FilterWriter</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
(which, even though it is 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>abstract</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">,
has no subclasses and so appears to have been put in either as a placeholder or
simply so you wouldn&#8217;t wonder where it was). However, the interfaces to
the classes are quite a close match and it&#8217;s apparent that you&#8217;re
supposed to use the new versions instead of the old whenever possible (that is,
except in cases where you&#8217;re forced to produce a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Stream</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
instead of a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Reader</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
123

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