Java Doc for StrLookup.java in  » Library » Apache-common-lang » org » apache » commons » lang » text » Java Source Code / Java DocumentationJava Source Code and Java Documentation

This class represents the simplest form of a string to string map. It has a benefit over a map in that it can create the result on demand based on the key.

This class comes complete with various factory methods. If these do not suffice, you can subclass and implement your own matcher.

For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the value on demand from the database
author:
   Stephen Colebourne
since:
   2.2
version:
   $Id: StrLookup.java 437554 2006-08-28 06:21:41Z bayard $

The internal implementation may use any mechanism to return the value. The simplest implementation is to use a Map.

The internal implementation may use any mechanism to return the value. The simplest implementation is to use a Map. However, virtually any implementation is possible.

For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the value on demand from the database Or, a numeric based implementation could be created that treats the key as an integer, increments the value and return the result as a string - converting 1 to 2, 15 to 16 etc.
Parameters:
  key - the key to be looked up, may be null the matching value, null if no match

If the map is null, then null will be returned from every lookup. The map result object is converted to a string using toString().
Parameters:
  map - the map of keys to values, may be null a lookup using the map, not null

If a security manager blocked access to system properties, then null will be returned from every lookup.

If a null key is used, this lookup will throw a NullPointerException. a lookup using system properties, not null