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
  `String`
  `lookup(String key)`
  Looks up a String key to provide a String value.

- ## Method Details

  - ### lookup

    String lookup(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.