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<a href="http://www.bruceeckel.com/javabook.html">Bruce Eckel's Thinking in Java</a>
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<H2 ALIGN=LEFT>
You
manipulate objects 
<P>with
handles 
</H2>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Each
programming language has its own means of manipulating data. Sometimes the
programmer must constantly be aware of what type of manipulation is going on.
Are you manipulating the object directly or are you dealing with some kind of
indirect representation (a pointer in C or C++) that must be treated with a
special syntax?
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">All
this is simplified in Java. You treat everything as an object, so there is a
single consistent syntax that you use everywhere. Although you 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><I>treat
</I></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">everything
as an object, the identifier you manipulate is actually a &#8220;handle&#8221;
to an object. (You might see this called a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><I>reference</I></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
or even a pointer in other discussions of Java.) You might imagine this scene
as a television (the object) with your remote control (the handle). As long as
you&#8217;re holding this handle, you have a connection to the television, but
when someone says &#8220;change the channel&#8221; or &#8220;lower the
volume,&#8221; what you&#8217;re manipulating is the handle, which in turn
modifies the object. If you want to move around the room and still control the
television, you take the remote/handle with you, not the television.
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Also,
the remote control can stand on its own, with no television. That is, just
because you have a handle doesn&#8217;t mean there&#8217;s necessarily an
object connected to it. So if you want to hold a word or sentence, you create a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>String</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
handle:
</FONT><P></DIV><DIV ALIGN=LEFT><TT><FONT FACE="Courier New" SIZE=3 COLOR="Black">String
s;
</FONT></TT><P></DIV><DIV ALIGN=LEFT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">But
here you&#8217;ve created 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><I>only</I></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
the handle, not an object. If you decided to send a message to 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>s</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
at this point, you&#8217;ll get an error (at run-time) because 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>s</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
isn&#8217;t actually attached to anything (there&#8217;s no television). A
safer practice, then, is always to initialize a handle when you create it:
</FONT><P></DIV><DIV ALIGN=LEFT><TT><FONT FACE="Courier New" SIZE=3 COLOR="Black">String
s = "asdf";
</FONT></TT><P></DIV><DIV ALIGN=LEFT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">However,
this uses a special case: strings can be initialized with quoted text.
Normally, you must use a more general type of initialization for objects.
</FONT><a name="_Toc375545218"></a><a name="_Toc408018419"></a><P></DIV>

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