Re: merging equal code (exercise in refactoring)
Eric Sosman <Eric.Sosman@sun.com> writes:
return format(source.toArray(
new java.lang.CharSequence[source.size()]);
A dual solution using Arrays.asList() is also possible.
This answer is better than my own, because it requires
the least amount of work of the programmer.
When a list is copied to an array or an array is copied
to a list, this needs O(n) operations. Therefore, I have
hesitated to use this myself. But a programmer's time
usually is more expensive than a processor's time.
My own solution tries to avoid an additional copy operation.
The code given was like
public static java.lang.CharSequence format
( PARAMETERS )
{ PREPARATION
for( LOOP_CONTROL )LOOP_STATEMENT
COMPLETION }
The ?LOOP_CONTROL? varied with ?PARAMETERS?, while
?PREPARATION?, ?LOOP_STATEMENT? and ?COMPLETION?
did not change.
When something varies with a parameter, the usual
solution is to make this a parameter, too.
But in Java, the LOOP_CONTROL of a for(:) statement
can not be used as a parameter (it would have to be
something like ?quoted code?).
So one has to invert the usual procedure and to make
everything else /except/ the loop control the ?parameter?.
This can be done by creating an object for the
PREPARATION, LOOP_STATEMENT and COMPLETION.
Then the two redundant method declarations become:
public static java.lang.CharSequence format
( LIST_PARAMETER )
{ final Delegate delegate = new Delegate();
for( LIST_LOOP_CONTROL )delegate.loopStatement( /* ... */ );
return delegate.completion(); }
public static java.lang.CharSequence format
( ARRAY_PARAMETER )
{ final Delegate delegate = new Delegate();
for( ARRAY_LOOP_CONTROL )delegate.loopStatement( /* ... */ );
return delegate.completion(); }
There still is some redundancy, but most of the formerly
duplicate code now has a single position within the
declaration of the Delegate class.
The actual code is following. As an additional benefit,
the code now is split into more method declarations
than before, which gives more anchor points for documentation.
class Util
{
public static java.lang.String indent( final java.lang.String text )
{ final java.lang.String text1 = text.replaceAll( "\n", "\n " );
return text1; }
public static java.lang.CharSequence format
( final java.lang.CharSequence[] source )
{ final Util util = new Util();
for( final java.lang.CharSequence component : source )
util.process( component );
return util.complete(); }
public static java.lang.CharSequence format
( final java.util.List<java.lang.CharSequence> source )
{ final Util util = new Util();
for( final java.lang.CharSequence component : source )
util.process( component );
return util.complete(); }
private final java.lang.StringBuilder result;
private final java.lang.StringBuilder text;
private boolean first;
public Util()
{ this.result = new java.lang.StringBuilder();
this.result.append( "Listing:\n" );
this.text = new java.lang.StringBuilder();
this.text.append( "[ " );
this.first = true; }
public void process( final java.lang.CharSequence component )
{ if( this.first )this.first = false;
else this.text.append( "\n" );
this.text.append( component ); }
public java.lang.CharSequence complete()
{ final char last = this.text.charAt( this.text.length() - 1 );
boolean space = true;
switch( last ){ case ' ': case ']': space = false; }
this.text.append( space ? " ]" : "]" );
this.result.append( indent( this.text.toString() ));
return result; }}