Package org.apache.commons.text.lookup

Interface StringLookup

All Known Subinterfaces:

BiStringLookup<U>

All Known Implementing Classes:

StrLookup

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface StringLookup

Lookups a String key for a String value.

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.

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:

1.3

Method Summary

Modifier and Type	Method	Description
java.lang.String	lookup(java.lang.String key)	Looks up a String key to provide a String value.

Method Detail

lookup

java.lang.String lookup(java.lang.String key)

Looks up a String key to provide a String value.

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.

This method always returns a String, regardless of the underlying data, by converting it as necessary. For example:

 Map<String, Object> map = new HashMap<String, Object>();
 map.put("number", new Integer(2));
 assertEquals("2", StringLookupFactory.mapStringLookup(map).lookup("number"));
 

Parameters:

key - the key to look up, may be null.

Returns:

The matching value, null if no match.