Avoiding the Urge to Sort
Problem
Your data needs to be sorted, but you don’t want to stop and sort it periodically.
Solution
Not everything that requires order requires an explicit sort operation. Just keep the data sorted at all times.
Discussion
You can avoid the overhead and elapsed time of an explicit sorting
operation by ensuring that the data is in the correct order at all
times. You can do this manually or, in Java 2, by using a
TreeSet
or a
TreeMap
. First, some code from a call tracking
program that I first wrote on JDK 1.0 to keep track of people I had
extended contact with. Far less functional than a Rolodex, my
CallTrak
program maintained a list of people
sorted by last name and first name. For each person it also had the
city, phone number, and email address. Here is a portion of the code
that was the event handler for the New User push button:
/** The list of User objects. */ Vector usrList = new Vector( ); /** The scrolling list */ java.awt.List visList = new List( ); /** Add one (new) Candidate to the lists */ protected void add(Candidate c) { String n = c.lastname; int i; for (i=0; i<usrList.size( ); i++) if (n.compareTo(((Candidate)(usrList.elementAt(i))).lastname) <= 0) break; visList.add(c.getName( ), i); usrList.insertElementAt(c, i); visList.select(i); // ensure current }
This code uses the String
class
compareTo(String)
routine. This has the same name and
signature as the compareTo(Object)
in
Comparable
, but was added to the
String
class in JDK 1.1, before the ...
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