Package org.apache.commons.text.lookup

Class BiFunctionStringLookup<P,​R>

  • Type Parameters:
    R - A function's return type
    P - A function's second input type
    All Implemented Interfaces:
    BiStringLookup<P>, StringLookup
    final class BiFunctionStringLookup<P,​R>
extends Object
implements BiStringLookup<P>
    A function-based lookup where the request for a lookup is answered by applying that function with a key.
    Since:
    1.9

    • Method Detail

      • on

        static <U,​T> BiFunctionStringLookup<U,​T> on​(BiFunction<String,​U,​T> biFunction)
        Creates a new instance backed by a Function.
        Type Parameters:
        T - the function's input type
        Parameters:
        biFunction - the function, may be null.
        Returns:
        a new instance backed by the given function.

      • on

        static <U,​T> BiFunctionStringLookup<U,​T> on​(Map<String,​T> map)
        Creates a new instance backed by a Map. Used by the default lookup.
        Type Parameters:
        T - the map's value type.
        Parameters:
        map - the map of keys to values, may be null.
        Returns:
        a new instance backed by the given map.

      • lookup

        public String lookup​(String key)
        Description copied from interface: StringLookup
        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"));
        Specified by:
        lookup in interface StringLookup
        Parameters:
        key - the key to look up, may be null.
        Returns:
        The matching value, null if no match.

      • lookup

        public String lookup​(String key,
                     P object)
        Looks up a String key by applying the function.

        If the function is null, then null is returned. The function result object is converted to a string using toString().

        Specified by:
        lookup in interface BiStringLookup<P>
        Parameters:
        key - the key to be looked up, may be null.
        object - ignored by default.
        Returns:
        The function result as a string, may be null.