Package: groovy.transform

## [Java] Annotation Type Memoized

- groovy.transform.Memoized

-     @Documented
      @Retention(RetentionPolicy.SOURCE)
      @Target({ ElementType.METHOD })
      @GroovyASTTransformationClass("org.codehaus.groovy.transform.MemoizedASTTransformation")
      public @interface Memoized

  Method annotation that creates a cache for the results of the execution of the annotated method. Whenever the method is called, the mapping between the parameters and the return value is preserved in a cache making subsequent calls with the same arguments fast.

  Example usage:

       class MemoizedExample {

           @Memoized
           int sum(int n1, int n2) {
               println "$n1 + $n2 = ${n1 + n2}"
               n1 + n2
           }
       }

  which becomes (approximately):

       class MemoizedExample {

           private final Closure memoizedSum = { int n1, int n2 ->
               private$method$memoizedSum(n1,n2)
           }.memoize()

           int sum(int n1, int n2) {
               memoizedSum(n1, n2)
           }

           private private$method$memoizedSum(int n1, int n2) {
               println "$n1 + $n2 = ${n1 + n2}"
               n1 + n2
           }
       }

  Upon execution of this code:

       def instance = new MemoizedExample()
       println instance.sum(1, 2)
       println instance.sum(1, 2)
       println instance.sum(2, 3)
       println instance.sum(2, 3)

  The following will be output:

       1 + 2 = 3
       3
       3
       2 + 3 = 5
       5
       5

  More examples:

       import groovy.transform.*

       // Script variable which is changed when increment()
       // method is invoked.
       // If cached method call is invoked then the value
       // of this variable will not change.
       @Field boolean incrementChange = false

       @Memoized
       int increment(int value) {
           incrementChange = true
           value + 1
       }

       // Invoke increment with argument 10.
       increment(10)

       // increment is invoked so incrementChange is true.
       assert incrementChange

       // Set incrementChange back to false.
       incrementChange = false

       // Invoke increment with argument 10.
       increment(10)

       // Now the cached method is used and
       // incrementChange is not changed.
       assert !incrementChange

       // Invoke increment with other argument value.
       increment(11)

       // increment is invoked so incrementChange is true.
       assert incrementChange

  Since:
    2.2.0

- - ### Element Summary

    Optional Element Summary
    Type | Name and Description
    --- | ---
    `int` | `maxCacheSize` The maximum size the cache can grow to.
    `int` | `protectedCacheSize` Number of cached return values to protect from garbage collection.

  - ### Inherited Methods Summary

    Inherited Methods
    Methods inherited from class | Name
    --- | ---
    `class Object` | `wait, wait, wait, equals, toString, hashCode, getClass, notify, notifyAll`

- - ### Element Detail

    - #### public int maxCacheSize

      The maximum size the cache can grow to.

      Default:
        0

    - #### public int protectedCacheSize

      Number of cached return values to protect from garbage collection.

      Default:
        0