org.apache.commons.lang.text
public abstract class StrLookup extends Object
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
Since: 2.2
Version: $Id: StrLookup.java 592077 2007-11-05 16:47:10Z mbenson $
Constructor Summary | |
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protected | StrLookup()
Constructor. |
Method Summary | |
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abstract String | lookup(String key)
Looks up a String key to a String value.
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static StrLookup | mapLookup(Map map)
Returns a lookup which looks up values using a map.
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static StrLookup | noneLookup()
Returns a lookup which always returns null.
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static StrLookup | systemPropertiesLookup()
Returns a lookup which uses System#getProperties() System properties
to lookup the key to value.
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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
Returns: 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
Returns: a lookup using the map, not null
Returns: a lookup that always returns null, not null
System#getProperties() System properties
to lookup the key to value.
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.
Returns: a lookup using system properties, not null