com.atlassian.jira.util
Class Functions

java.lang.Object
  com.atlassian.jira.util.Functions

public class Functions
extends Object

Useful standard functions.

Constructor Summary

Functions()

Method Summary

static <S,T extends S> Function<T,S>	coerceToSuper() Transform to a super class.
static <T,R extends T> Function<T,R>	downcast(Class<R> subclass) Get a function that always the input downcast to the supplied class.
static <T> Function<T,T>	identity() Get a function that always returns the input.
static <T,R> Function<T,R>	memoize(Function<T,R> function, ConcurrentMap<T,R> map) Memoizer maps an input to an output and always returns the mapped result rather than calling the wrapped function every time.
static <T,R> com.google.common.base.Function<T,R>	toGoogleFunction(Function<T,R> delegate) Map to a google-collections Function.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Functions

public Functions()

Method Detail

memoize

public static <T,R> Function<T,R> memoize(Function<T,R> function,
                                          ConcurrentMap<T,R> map)

Memoizer maps an input to an output and always returns the mapped result rather than calling the wrapped function every time. Useful when the wrapped function is expensive to call.

Note, once mapped the input and the result can only be externally removed. Also, if the supplied function returns nulls then no memoization will occur.

Type Parameters:

T - the input type. MUST be immutable.

R - the result type.

Parameters:

function - for supplying the initial value that gets mapped

map - for storing the key-value mappings

Returns:

a memoizing function.

identity

public static <T> Function<T,T> identity()

Get a function that always returns the input.

Type Parameters:

T - the type of the input and the output for the function.

Returns:

the identity function.

downcast

public static <T,R extends T> Function<T,R> downcast(Class<R> subclass)

Get a function that always the input downcast to the supplied class.

Type Parameters:

T - the type of the input and the output for the function.

Returns:

the identity function.

coerceToSuper

public static <S,T extends S> Function<T,S> coerceToSuper()

Transform to a super class. Usually needs to be called with explicit type parameters, eg: Functions.<SuperClass, SubClass> coerceToSuper();

Type Parameters:

S - the super class.

T - the sub class.

toGoogleFunction

public static <T,R> com.google.common.base.Function<T,R> toGoogleFunction(Function<T,R> delegate)

Map to a google-collections Function.

Type Parameters:

T - input type

R - output type

Parameters:

input - the function to map

Returns:

the mapped function.