Function (Guava: Google Core Libraries for Java HEAD-android-SNAPSHOT API)

All Known Subinterfaces:

LoadingCache<K,V>

All Known Implementing Classes:

AbstractLoadingCache, Converter, ForwardingLoadingCache, ForwardingLoadingCache.SimpleForwardingLoadingCache
```
@GwtCompatible
public interface Function<F extends @Nullable java.lang.Object,T extends @Nullable java.lang.Object>
```
Determines an output value based on an input value; a pre-Java-8 version of java.util.function.Function.
The Functions class provides common functions and related utilities.
See the Guava User Guide article on the use of Function.
For Java 8+ users

This interface is now a legacy type. Use java.util.function.Function (or the appropriate primitive specialization such as ToIntFunction) instead whenever possible. Otherwise, at least reduce explicit dependencies on this type by using lambda expressions or method references instead of classes, leaving your code easier to migrate in the future.
To use an existing function (say, named function) in a context where the other type of function is expected, use the method reference function::apply. A future version of com.google.common.base.Function will be made to extend java.util.function.Function, making conversion code necessary only in one direction. At that time, this interface will be officially discouraged.

Since:

2.0

Author:

Kevin Bourrillion

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`T`	`apply(F input)`	Returns the result of applying this function to `input`.
`boolean`	`equals(java.lang.Object object)`	May return `true` if `object` is a `Function` that behaves identically to this function.

- Method Detail
  - apply
```
T apply(F input)
```
    Returns the result of applying this function to input. This method is generally expected, but not absolutely required, to have the following properties:
    
    Its execution does not cause any observable side effects.
    The computation is consistent with equals; that is, Objects.equal(a, b) implies that Objects.equal(function.apply(a), function.apply(b)).
    Throws:
    
    java.lang.NullPointerException - if input is null and this function does not accept null arguments
  - equals
```
boolean equals(@CheckForNull
               java.lang.Object object)
```
    May return true if object is a Function that behaves identically to this function.
    Warning: do not depend on the behavior of this method.
    Historically, Function instances in this library have implemented this method to recognize certain cases where distinct Function instances would in fact behave identically. However, as code migrates to java.util.function, that behavior will disappear. It is best not to depend on it.
    
    Overrides:
    
    equals in class java.lang.Object