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<h1 ALIGN=center> Java Style to Avoid </h1>






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<p>
This page contains a list of various things I've encountered in students'
programs in this and past semesters
that might better be avoided.  Expect it to expand from
time to time.
</p>

<p>

<a href="#string_const"><b>* String constructors are seldom necessary.</b></a> <br>



<a href="#compare_true"><b>* Boolean values need not be compared to <code>true</code> or 
     <code>false</code>.</b></a> <br>



<a href="#assign_bool"><b>* Boolean variables may be assigned from arbitrary boolean 
     expressions.</b></a> <br>


<a href="#bad_throws"><b>* Throws clauses aren't intended just to shut up the
     Java compiler.</b></a> <br>


<a href="#specific_exceptions"><b>* Be specific about exceptions.</b></a> <br>


<a href="#commenting_out"><b>* Don't leave commented-out regions of code.</b></a> <br>




<p>
<div style="width: 50%; position: relative; left: 25%">  <hr> </div>
<p>
<a name="string_const"> <b>String constructors are seldom necessary.</b></a>
Write
<pre>
    String aString = "foo";
</pre>
not 
<pre>
    String aString = new String ("foo");   <span class="bad">// BAD</span>
</pre>
<p>

<p>
<div style="width: 50%; position: relative; left: 25%">  <hr> </div>
<p>
<a name="compare_true"> <b>Boolean values need not be compared to <code>true</code> or 
     <code>false</code>.</b></a>
Rather than writing
<pre>
    if (isRound == true &amp;&amp; isFilled == false)  <span class="bad">// BAD</span>
        ...
</pre>
write
<pre>
    if (isRound &amp;&amp; ! isFilled)
        ...
</pre>
Of course, to make this work, you should choose names for things that contain
or return booleans that suggest that they <em>are</em> boolean.  For example,
names like <code>isRound</code>, <code>hasNext</code>, 
<code>amProcessing</code> clearly suggest that their values are boolean.

<p>

<p>
<div style="width: 50%; position: relative; left: 25%">  <hr> </div>
<p>
<a name="assign_bool"> <b>Boolean variables may be assigned from arbitrary boolean 
     expressions.</b></a>
Rather than writing
<pre>
    if (! isFilled)             <span class="bad">// BAD</span>
        isOutline = true;
    else
        isOutline = false;
</pre>
simply write
<pre>
    isOutline = !isFilled;
</pre>

<p>

<p>
<div style="width: 50%; position: relative; left: 25%">  <hr> </div>
<p>
<a name="bad_throws"> <b>Throws clauses aren't intended just to shut up the
     Java compiler.</b></a>
Unless you are writing a throw-away piece of code to
     try out something, avoid things like:
<pre>
     public static void main (String[] args) throws IOException <span class="bad">// BAD</span>
</pre>
If <code>javac</code> was complaining before you did this, it means 
that something in your code might crash the program by 
throwing <code>IOException</code>.  Decide what you want to do in that case and
put in a <code>try...catch</code> block.

<p>

<p>
<div style="width: 50%; position: relative; left: 25%">  <hr> </div>
<p>
<a name="specific_exceptions"> <b>Be specific about exceptions.</b></a>
In most cases, it is unwise to write
<pre>
     try {
        doSomething ();
     } catch (Exception e) {     <span class="bad">// BAD</span>
        saySomething ();
     }
</pre>
This will catch all exceptions, including things like 
<code>NullPointerException</code>, which is more often a programming error
rather than an expected result of user errors.  Try to narrow things down.

<p>

<p>
<div style="width: 50%; position: relative; left: 25%">  <hr> </div>
<p>
<a name="commenting_out"> <b>Don't leave commented-out regions of code.</b></a>
There is nothing more ugly (or difficult to read) than sections of program
text that look like this:
<pre>
     foo (x, y);
 //  foo (0, 0);
 //    if (x > y) {
 //        ...
 //   }
     return null;
</pre>
Clean them up before you submit.  In fact, don't have them there in the 
first place.  With version control, you have all your old versions of 
code around in the repository, should you ever need to restore them.
<p>


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